diff --git a/script/tool/analysis_options.yaml b/script/tool/analysis_options.yaml
deleted file mode 100644
index cda4f6e153e6..000000000000
--- a/script/tool/analysis_options.yaml
+++ /dev/null
@@ -1 +0,0 @@
-include: ../../analysis_options_legacy.yaml
diff --git a/script/tool/lib/src/analyze_command.dart b/script/tool/lib/src/analyze_command.dart
index 9489303f5665..e22bb0b17ba5 100644
--- a/script/tool/lib/src/analyze_command.dart
+++ b/script/tool/lib/src/analyze_command.dart
@@ -9,7 +9,9 @@ import 'package:path/path.dart' as p;
 
 import 'common.dart';
 
+/// A command to run Dart analysis on packages.
 class AnalyzeCommand extends PluginCommand {
+  /// Creates a analysis command instance.
   AnalyzeCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -31,9 +33,7 @@ class AnalyzeCommand extends PluginCommand {
       'This command requires "pub" and "flutter" to be in your path.';
 
   @override
-  Future<Null> run() async {
-    checkSharding();
-
+  Future<void> run() async {
     print('Verifying analysis settings...');
     final List<FileSystemEntity> files = packagesDir.listSync(recursive: true);
     for (final FileSystemEntity file in files) {
@@ -42,8 +42,8 @@ class AnalyzeCommand extends PluginCommand {
         continue;
       }
 
-      final bool allowed = argResults[_customAnalysisFlag].any(
-          (String directory) =>
+      final bool allowed = (argResults[_customAnalysisFlag] as List<String>)
+          .any((String directory) =>
               directory != null &&
               directory.isNotEmpty &&
               p.isWithin(p.join(packagesDir.path, directory), file.path));
@@ -62,7 +62,7 @@ class AnalyzeCommand extends PluginCommand {
         'pub', <String>['global', 'activate', 'tuneup'],
         workingDir: packagesDir, exitOnError: true);
 
-    await for (Directory package in getPackages()) {
+    await for (final Directory package in getPackages()) {
       if (isFlutterPackage(package, fileSystem)) {
         await processRunner.runAndStream('flutter', <String>['packages', 'get'],
             workingDir: package, exitOnError: true);
@@ -73,7 +73,7 @@ class AnalyzeCommand extends PluginCommand {
     }
 
     final List<String> failingPackages = <String>[];
-    await for (Directory package in getPlugins()) {
+    await for (final Directory package in getPlugins()) {
       final int exitCode = await processRunner.runAndStream(
           'pub', <String>['global', 'run', 'tuneup', 'check'],
           workingDir: package);
@@ -85,9 +85,9 @@ class AnalyzeCommand extends PluginCommand {
     print('\n\n');
     if (failingPackages.isNotEmpty) {
       print('The following packages have analyzer errors (see above):');
-      failingPackages.forEach((String package) {
+      for (final String package in failingPackages) {
         print(' * $package');
-      });
+      }
       throw ToolExit(1);
     }
 
diff --git a/script/tool/lib/src/build_examples_command.dart b/script/tool/lib/src/build_examples_command.dart
index 966fdc9b99df..0069c0586810 100644
--- a/script/tool/lib/src/build_examples_command.dart
+++ b/script/tool/lib/src/build_examples_command.dart
@@ -11,7 +11,9 @@ import 'package:platform/platform.dart';
 
 import 'common.dart';
 
+/// A command to build the example applications for packages.
 class BuildExamplesCommand extends PluginCommand {
+  /// Creates an instance of the build command.
   BuildExamplesCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -39,33 +41,40 @@ class BuildExamplesCommand extends PluginCommand {
       'This command requires "flutter" to be in your path.';
 
   @override
-  Future<Null> run() async {
-    if (!argResults[kIpa] &&
-        !argResults[kApk] &&
-        !argResults[kLinux] &&
-        !argResults[kMacos] &&
-        !argResults[kWeb] &&
-        !argResults[kWindows]) {
-      print('None of --linux, --macos, --web, --windows, --apk, or --ipa were '
-          'specified, so not building anything.');
+  Future<void> run() async {
+    final List<String> platformSwitches = <String>[
+      kApk,
+      kIpa,
+      kLinux,
+      kMacos,
+      kWeb,
+      kWindows,
+    ];
+    final Map<String, bool> platforms = <String, bool>{
+      for (final String platform in platformSwitches)
+        platform: argResults[platform] as bool
+    };
+    if (!platforms.values.any((bool enabled) => enabled)) {
+      print(
+          'None of ${platformSwitches.map((String platform) => '--$platform').join(', ')} '
+          'were specified, so not building anything.');
       return;
     }
     final String flutterCommand =
-        LocalPlatform().isWindows ? 'flutter.bat' : 'flutter';
+        const LocalPlatform().isWindows ? 'flutter.bat' : 'flutter';
 
-    final String enableExperiment = argResults[kEnableExperiment];
+    final String enableExperiment = argResults[kEnableExperiment] as String;
 
-    checkSharding();
     final List<String> failingPackages = <String>[];
-    await for (Directory plugin in getPlugins()) {
-      for (Directory example in getExamplesForPlugin(plugin)) {
+    await for (final Directory plugin in getPlugins()) {
+      for (final Directory example in getExamplesForPlugin(plugin)) {
         final String packageName =
             p.relative(example.path, from: packagesDir.path);
 
-        if (argResults[kLinux]) {
+        if (platforms[kLinux]) {
           print('\nBUILDING Linux for $packageName');
           if (isLinuxPlugin(plugin, fileSystem)) {
-            int buildExitCode = await processRunner.runAndStream(
+            final int buildExitCode = await processRunner.runAndStream(
                 flutterCommand,
                 <String>[
                   'build',
@@ -82,10 +91,10 @@ class BuildExamplesCommand extends PluginCommand {
           }
         }
 
-        if (argResults[kMacos]) {
+        if (platforms[kMacos]) {
           print('\nBUILDING macOS for $packageName');
           if (isMacOsPlugin(plugin, fileSystem)) {
-            int exitCode = await processRunner.runAndStream(
+            final int exitCode = await processRunner.runAndStream(
                 flutterCommand,
                 <String>[
                   'build',
@@ -102,10 +111,10 @@ class BuildExamplesCommand extends PluginCommand {
           }
         }
 
-        if (argResults[kWeb]) {
+        if (platforms[kWeb]) {
           print('\nBUILDING web for $packageName');
           if (isWebPlugin(plugin, fileSystem)) {
-            int buildExitCode = await processRunner.runAndStream(
+            final int buildExitCode = await processRunner.runAndStream(
                 flutterCommand,
                 <String>[
                   'build',
@@ -122,10 +131,10 @@ class BuildExamplesCommand extends PluginCommand {
           }
         }
 
-        if (argResults[kWindows]) {
+        if (platforms[kWindows]) {
           print('\nBUILDING Windows for $packageName');
           if (isWindowsPlugin(plugin, fileSystem)) {
-            int buildExitCode = await processRunner.runAndStream(
+            final int buildExitCode = await processRunner.runAndStream(
                 flutterCommand,
                 <String>[
                   'build',
@@ -142,7 +151,7 @@ class BuildExamplesCommand extends PluginCommand {
           }
         }
 
-        if (argResults[kIpa]) {
+        if (platforms[kIpa]) {
           print('\nBUILDING IPA for $packageName');
           if (isIosPlugin(plugin, fileSystem)) {
             final int exitCode = await processRunner.runAndStream(
@@ -163,7 +172,7 @@ class BuildExamplesCommand extends PluginCommand {
           }
         }
 
-        if (argResults[kApk]) {
+        if (platforms[kApk]) {
           print('\nBUILDING APK for $packageName');
           if (isAndroidPlugin(plugin, fileSystem)) {
             final int exitCode = await processRunner.runAndStream(
@@ -188,7 +197,7 @@ class BuildExamplesCommand extends PluginCommand {
 
     if (failingPackages.isNotEmpty) {
       print('The following build are failing (see above for details):');
-      for (String package in failingPackages) {
+      for (final String package in failingPackages) {
         print(' * $package');
       }
       throw ToolExit(1);
diff --git a/script/tool/lib/src/common.dart b/script/tool/lib/src/common.dart
index 7d3063a20f53..fc1fdca6a1cd 100644
--- a/script/tool/lib/src/common.dart
+++ b/script/tool/lib/src/common.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io' as io;
 import 'dart:math';
 
@@ -15,7 +16,9 @@ import 'package:path/path.dart' as p;
 import 'package:pub_semver/pub_semver.dart';
 import 'package:yaml/yaml.dart';
 
-typedef void Print(Object object);
+/// The signature for a print handler for commands that allow overriding the
+/// print destination.
+typedef Print = void Function(Object object);
 
 /// Key for windows platform.
 const String kWindows = 'windows';
@@ -53,8 +56,9 @@ bool isFlutterPackage(FileSystemEntity entity, FileSystem fileSystem) {
   try {
     final File pubspecFile =
         fileSystem.file(p.join(entity.path, 'pubspec.yaml'));
-    final YamlMap pubspecYaml = loadYaml(pubspecFile.readAsStringSync());
-    final YamlMap dependencies = pubspecYaml['dependencies'];
+    final YamlMap pubspecYaml =
+        loadYaml(pubspecFile.readAsStringSync()) as YamlMap;
+    final YamlMap dependencies = pubspecYaml['dependencies'] as YamlMap;
     if (dependencies == null) {
       return false;
     }
@@ -89,16 +93,17 @@ bool pluginSupportsPlatform(
   try {
     final File pubspecFile =
         fileSystem.file(p.join(entity.path, 'pubspec.yaml'));
-    final YamlMap pubspecYaml = loadYaml(pubspecFile.readAsStringSync());
-    final YamlMap flutterSection = pubspecYaml['flutter'];
+    final YamlMap pubspecYaml =
+        loadYaml(pubspecFile.readAsStringSync()) as YamlMap;
+    final YamlMap flutterSection = pubspecYaml['flutter'] as YamlMap;
     if (flutterSection == null) {
       return false;
     }
-    final YamlMap pluginSection = flutterSection['plugin'];
+    final YamlMap pluginSection = flutterSection['plugin'] as YamlMap;
     if (pluginSection == null) {
       return false;
     }
-    final YamlMap platforms = pluginSection['platforms'];
+    final YamlMap platforms = pluginSection['platforms'] as YamlMap;
     if (platforms == null) {
       // Legacy plugin specs are assumed to support iOS and Android.
       if (!pluginSection.containsKey('platforms')) {
@@ -153,12 +158,16 @@ void printErrorAndExit({@required String errorMessage, int exitCode = 1}) {
 
 /// Error thrown when a command needs to exit with a non-zero exit code.
 class ToolExit extends Error {
+  /// Creates a tool exit with the given [exitCode].
   ToolExit(this.exitCode);
 
+  /// The code that the process should exit with.
   final int exitCode;
 }
 
-abstract class PluginCommand extends Command<Null> {
+/// Interface definition for all commands in this tool.
+abstract class PluginCommand extends Command<void> {
+  /// Creates a command to operate on [packagesDir] with the given environment.
   PluginCommand(
     this.packagesDir,
     this.fileSystem, {
@@ -230,23 +239,25 @@ abstract class PluginCommand extends Command<Null> {
   int _shardIndex;
   int _shardCount;
 
+  /// The shard of the overall command execution that this instance should run.
   int get shardIndex {
     if (_shardIndex == null) {
-      checkSharding();
+      _checkSharding();
     }
     return _shardIndex;
   }
 
+  /// The number of shards this command is divided into.
   int get shardCount {
     if (_shardCount == null) {
-      checkSharding();
+      _checkSharding();
     }
     return _shardCount;
   }
 
-  void checkSharding() {
-    final int shardIndex = int.tryParse(argResults[_shardIndexArg]);
-    final int shardCount = int.tryParse(argResults[_shardCountArg]);
+  void _checkSharding() {
+    final int shardIndex = int.tryParse(argResults[_shardIndexArg] as String);
+    final int shardCount = int.tryParse(argResults[_shardCountArg] as String);
     if (shardIndex == null) {
       usageException('$_shardIndexArg must be an integer');
     }
@@ -281,7 +292,7 @@ abstract class PluginCommand extends Command<Null> {
     final int start = min(shardIndex * shardSize, allPlugins.length);
     final int end = min(start + shardSize, allPlugins.length);
 
-    for (Directory plugin in allPlugins.sublist(start, end)) {
+    for (final Directory plugin in allPlugins.sublist(start, end)) {
       yield plugin;
     }
   }
@@ -301,25 +312,28 @@ abstract class PluginCommand extends Command<Null> {
   ///    "client library" package, which declares the API for the plugin, as
   ///    well as one or more platform-specific implementations.
   Stream<Directory> _getAllPlugins() async* {
-    Set<String> plugins = Set<String>.from(argResults[_pluginsArg]);
+    Set<String> plugins =
+        Set<String>.from(argResults[_pluginsArg] as List<String>);
     final Set<String> excludedPlugins =
-        Set<String>.from(argResults[_excludeArg]);
-    final bool runOnChangedPackages = argResults[_runOnChangedPackagesArg];
+        Set<String>.from(argResults[_excludeArg] as List<String>);
+    final bool runOnChangedPackages =
+        argResults[_runOnChangedPackagesArg] as bool;
     if (plugins.isEmpty && runOnChangedPackages) {
       plugins = await _getChangedPackages();
     }
 
-    await for (FileSystemEntity entity
+    await for (final FileSystemEntity entity
         in packagesDir.list(followLinks: false)) {
       // A top-level Dart package is a plugin package.
       if (_isDartPackage(entity)) {
         if (!excludedPlugins.contains(entity.basename) &&
             (plugins.isEmpty || plugins.contains(p.basename(entity.path)))) {
-          yield entity;
+          yield entity as Directory;
         }
       } else if (entity is Directory) {
         // Look for Dart packages under this top-level directory.
-        await for (FileSystemEntity subdir in entity.list(followLinks: false)) {
+        await for (final FileSystemEntity subdir
+            in entity.list(followLinks: false)) {
           if (_isDartPackage(subdir)) {
             // If --plugin=my_plugin is passed, then match all federated
             // plugins under 'my_plugin'. Also match if the exact plugin is
@@ -334,7 +348,7 @@ abstract class PluginCommand extends Command<Null> {
                 (plugins.isEmpty ||
                     plugins.contains(relativePath) ||
                     plugins.contains(basenamePath))) {
-              yield subdir;
+              yield subdir as Directory;
             }
           }
         }
@@ -350,7 +364,7 @@ abstract class PluginCommand extends Command<Null> {
   /// Returns all Dart package folders (typically, plugin + example) of the
   /// plugins involved in this command execution.
   Stream<Directory> getPackages() async* {
-    await for (Directory plugin in getPlugins()) {
+    await for (final Directory plugin in getPlugins()) {
       yield plugin;
       yield* plugin
           .list(recursive: true, followLinks: false)
@@ -401,7 +415,7 @@ abstract class PluginCommand extends Command<Null> {
   /// Throws tool exit if [gitDir] nor root directory is a git directory.
   Future<GitVersionFinder> retrieveVersionFinder() async {
     final String rootDir = packagesDir.parent.absolute.path;
-    String baseSha = argResults[_kBaseSha];
+    final String baseSha = argResults[_kBaseSha] as String;
 
     GitDir baseGitDir = gitDir;
     if (baseGitDir == null) {
@@ -424,14 +438,14 @@ abstract class PluginCommand extends Command<Null> {
     final List<String> allChangedFiles =
         await gitVersionFinder.getChangedFiles();
     final Set<String> packages = <String>{};
-    allChangedFiles.forEach((String path) {
+    for (final String path in allChangedFiles) {
       final List<String> pathComponents = path.split('/');
       final int packagesIndex =
           pathComponents.indexWhere((String element) => element == 'packages');
       if (packagesIndex != -1) {
         packages.add(pathComponents[packagesIndex + 1]);
       }
-    });
+    }
     if (packages.isNotEmpty) {
       final String changedPackages = packages.join(',');
       print(changedPackages);
@@ -446,6 +460,7 @@ abstract class PluginCommand extends Command<Null> {
 /// We use this instead of directly running the process so it can be overridden
 /// in tests.
 class ProcessRunner {
+  /// Creates a new process runner.
   const ProcessRunner();
 
   /// Run the [executable] with [args] and stream output to stderr and stdout.
@@ -490,8 +505,8 @@ class ProcessRunner {
   Future<io.ProcessResult> run(String executable, List<String> args,
       {Directory workingDir,
       bool exitOnError = false,
-      stdoutEncoding = io.systemEncoding,
-      stderrEncoding = io.systemEncoding}) async {
+      Encoding stdoutEncoding = io.systemEncoding,
+      Encoding stderrEncoding = io.systemEncoding}) async {
     return io.Process.run(executable, args,
         workingDirectory: workingDir?.path,
         stdoutEncoding: stdoutEncoding,
@@ -569,15 +584,15 @@ class GitVersionFinder {
   Future<List<String>> getChangedFiles() async {
     final String baseSha = await _getBaseSha();
     final io.ProcessResult changedFilesCommand = await baseGitDir
-        .runCommand(<String>['diff', '--name-only', '$baseSha', 'HEAD']);
+        .runCommand(<String>['diff', '--name-only', baseSha, 'HEAD']);
     print('Determine diff with base sha: $baseSha');
-    final String changedFilesStdout = changedFilesCommand.stdout.toString()  ?? '';
+    final String changedFilesStdout =
+        changedFilesCommand.stdout.toString() ?? '';
     if (changedFilesStdout.isEmpty) {
       return <String>[];
     }
-    final List<String> changedFiles = changedFilesStdout
-        .split('\n')
-          ..removeWhere((element) => element.isEmpty);
+    final List<String> changedFiles = changedFilesStdout.split('\n')
+      ..removeWhere((String element) => element.isEmpty);
     return changedFiles.toList();
   }
 
@@ -585,8 +600,8 @@ class GitVersionFinder {
   Future<Version> getPackageVersion(String pubspecPath, String gitRef) async {
     final io.ProcessResult gitShow =
         await baseGitDir.runCommand(<String>['show', '$gitRef:$pubspecPath']);
-    final String fileContent = gitShow.stdout;
-    final String versionString = loadYaml(fileContent)['version'];
+    final String fileContent = gitShow.stdout as String;
+    final String versionString = loadYaml(fileContent)['version'] as String;
     return versionString == null ? null : Version.parse(versionString);
   }
 
diff --git a/script/tool/lib/src/create_all_plugins_app_command.dart b/script/tool/lib/src/create_all_plugins_app_command.dart
index aaa7f7fb9667..4b5b4c6b8df4 100644
--- a/script/tool/lib/src/create_all_plugins_app_command.dart
+++ b/script/tool/lib/src/create_all_plugins_app_command.dart
@@ -12,7 +12,9 @@ import 'package:pubspec_parse/pubspec_parse.dart';
 
 import 'common.dart';
 
+/// A command to create an application that builds all in a single application.
 class CreateAllPluginsAppCommand extends PluginCommand {
+  /// Creates an instance of the builder command.
   CreateAllPluginsAppCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -36,7 +38,7 @@ class CreateAllPluginsAppCommand extends PluginCommand {
   String get name => 'all-plugins-app';
 
   @override
-  Future<Null> run() async {
+  Future<void> run() async {
     final int exitCode = await _createApp();
     if (exitCode != 0) {
       throw ToolExit(exitCode);
@@ -76,7 +78,7 @@ class CreateAllPluginsAppCommand extends PluginCommand {
     }
 
     final StringBuffer newGradle = StringBuffer();
-    for (String line in gradleFile.readAsLinesSync()) {
+    for (final String line in gradleFile.readAsLinesSync()) {
       newGradle.writeln(line);
       if (line.contains('defaultConfig {')) {
         newGradle.writeln('        multiDexEnabled true');
@@ -105,7 +107,7 @@ class CreateAllPluginsAppCommand extends PluginCommand {
     }
 
     final StringBuffer newManifest = StringBuffer();
-    for (String line in manifestFile.readAsLinesSync()) {
+    for (final String line in manifestFile.readAsLinesSync()) {
       if (line.contains('package="com.example.all_plugins"')) {
         newManifest
           ..writeln('package="com.example.all_plugins"')
@@ -149,7 +151,7 @@ class CreateAllPluginsAppCommand extends PluginCommand {
     final Map<String, PathDependency> pathDependencies =
         <String, PathDependency>{};
 
-    await for (Directory package in getPlugins()) {
+    await for (final Directory package in getPlugins()) {
       final String pluginName = package.path.split('/').last;
       final File pubspecFile =
           fileSystem.file(p.join(package.path, 'pubspec.yaml'));
@@ -183,15 +185,15 @@ dev_dependencies:${_pubspecMapString(pubspec.devDependencies)}
   String _pubspecMapString(Map<String, dynamic> values) {
     final StringBuffer buffer = StringBuffer();
 
-    for (MapEntry<String, dynamic> entry in values.entries) {
+    for (final MapEntry<String, dynamic> entry in values.entries) {
       buffer.writeln();
       if (entry.value is VersionConstraint) {
         buffer.write('  ${entry.key}: ${entry.value}');
       } else if (entry.value is SdkDependency) {
-        final SdkDependency dep = entry.value;
+        final SdkDependency dep = entry.value as SdkDependency;
         buffer.write('  ${entry.key}: \n    sdk: ${dep.sdk}');
       } else if (entry.value is PathDependency) {
-        final PathDependency dep = entry.value;
+        final PathDependency dep = entry.value as PathDependency;
         buffer.write('  ${entry.key}: \n    path: ${dep.path}');
       } else {
         throw UnimplementedError(
diff --git a/script/tool/lib/src/drive_examples_command.dart b/script/tool/lib/src/drive_examples_command.dart
index 54e0eee26425..e52052a49ae6 100644
--- a/script/tool/lib/src/drive_examples_command.dart
+++ b/script/tool/lib/src/drive_examples_command.dart
@@ -8,7 +8,9 @@ import 'package:path/path.dart' as p;
 import 'package:platform/platform.dart';
 import 'common.dart';
 
+/// A command to run the example applications for packages via Flutter driver.
 class DriveExamplesCommand extends PluginCommand {
+  /// Creates an instance of the drive command.
   DriveExamplesCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -48,20 +50,19 @@ class DriveExamplesCommand extends PluginCommand {
       'integration_test/*_test.dart.';
 
   @override
-  Future<Null> run() async {
-    checkSharding();
+  Future<void> run() async {
     final List<String> failingTests = <String>[];
-    final bool isLinux = argResults[kLinux];
-    final bool isMacos = argResults[kMacos];
-    final bool isWeb = argResults[kWeb];
-    final bool isWindows = argResults[kWindows];
-    await for (Directory plugin in getPlugins()) {
+    final bool isLinux = argResults[kLinux] == true;
+    final bool isMacos = argResults[kMacos] == true;
+    final bool isWeb = argResults[kWeb] == true;
+    final bool isWindows = argResults[kWindows] == true;
+    await for (final Directory plugin in getPlugins()) {
       final String flutterCommand =
-          LocalPlatform().isWindows ? 'flutter.bat' : 'flutter';
-      for (Directory example in getExamplesForPlugin(plugin)) {
+          const LocalPlatform().isWindows ? 'flutter.bat' : 'flutter';
+      for (final Directory example in getExamplesForPlugin(plugin)) {
         final String packageName =
             p.relative(example.path, from: packagesDir.path);
-        if (!(await pluginSupportedOnCurrentPlatform(plugin, fileSystem))) {
+        if (!(await _pluginSupportedOnCurrentPlatform(plugin, fileSystem))) {
           continue;
         }
         final Directory driverTests =
@@ -71,7 +72,7 @@ class DriveExamplesCommand extends PluginCommand {
           continue;
         }
         // Look for driver tests ending in _test.dart in test_driver/
-        await for (FileSystemEntity test in driverTests.list()) {
+        await for (final FileSystemEntity test in driverTests.list()) {
           final String driverTestName =
               p.relative(test.path, from: driverTests.path);
           if (!driverTestName.endsWith('_test.dart')) {
@@ -100,7 +101,7 @@ class DriveExamplesCommand extends PluginCommand {
                 fileSystem.directory(p.join(example.path, 'integration_test'));
 
             if (await integrationTests.exists()) {
-              await for (FileSystemEntity integration_test
+              await for (final FileSystemEntity integration_test
                   in integrationTests.list()) {
                 if (!integration_test.basename.endsWith('_test.dart')) {
                   continue;
@@ -125,7 +126,8 @@ Tried searching for the following:
 
           final List<String> driveArgs = <String>['drive'];
 
-          final String enableExperiment = argResults[kEnableExperiment];
+          final String enableExperiment =
+              argResults[kEnableExperiment] as String;
           if (enableExperiment.isNotEmpty) {
             driveArgs.add('--enable-experiment=$enableExperiment');
           }
@@ -157,10 +159,10 @@ Tried searching for the following:
             ]);
           }
 
-          for (final targetPath in targetPaths) {
+          for (final String targetPath in targetPaths) {
             final int exitCode = await processRunner.runAndStream(
                 flutterCommand,
-                [
+                <String>[
                   ...driveArgs,
                   '--driver',
                   p.join('test_driver', driverTestName),
@@ -180,7 +182,7 @@ Tried searching for the following:
 
     if (failingTests.isNotEmpty) {
       print('The following driver tests are failing (see above for details):');
-      for (String test in failingTests) {
+      for (final String test in failingTests) {
         print(' * $test');
       }
       throw ToolExit(1);
@@ -189,16 +191,16 @@ Tried searching for the following:
     print('All driver tests successful!');
   }
 
-  Future<bool> pluginSupportedOnCurrentPlatform(
+  Future<bool> _pluginSupportedOnCurrentPlatform(
       FileSystemEntity plugin, FileSystem fileSystem) async {
-    final bool isAndroid = argResults[kAndroid];
-    final bool isIOS = argResults[kIos];
-    final bool isLinux = argResults[kLinux];
-    final bool isMacos = argResults[kMacos];
-    final bool isWeb = argResults[kWeb];
-    final bool isWindows = argResults[kWindows];
+    final bool isAndroid = argResults[kAndroid] == true;
+    final bool isIOS = argResults[kIos] == true;
+    final bool isLinux = argResults[kLinux] == true;
+    final bool isMacos = argResults[kMacos] == true;
+    final bool isWeb = argResults[kWeb] == true;
+    final bool isWindows = argResults[kWindows] == true;
     if (isAndroid) {
-      return (isAndroidPlugin(plugin, fileSystem));
+      return isAndroidPlugin(plugin, fileSystem);
     }
     if (isIOS) {
       return isIosPlugin(plugin, fileSystem);
@@ -216,9 +218,9 @@ Tried searching for the following:
       return isWindowsPlugin(plugin, fileSystem);
     }
     // When we are here, no flags are specified. Only return true if the plugin
-    // supports Android for legacy command support. TODO(cyanglaz): Make Android
-    // flag also required like other platforms (breaking change).
-    // https://github.com/flutter/flutter/issues/58285
+    // supports Android for legacy command support.
+    // TODO(cyanglaz): Make Android flag also required like other platforms
+    // (breaking change). https://github.com/flutter/flutter/issues/58285
     return isAndroidPlugin(plugin, fileSystem);
   }
 }
diff --git a/script/tool/lib/src/firebase_test_lab_command.dart b/script/tool/lib/src/firebase_test_lab_command.dart
index 8e0abd507464..2998522da036 100644
--- a/script/tool/lib/src/firebase_test_lab_command.dart
+++ b/script/tool/lib/src/firebase_test_lab_command.dart
@@ -11,7 +11,9 @@ import 'package:uuid/uuid.dart';
 
 import 'common.dart';
 
+/// A command to run tests via Firebase test lab.
 class FirebaseTestLabCommand extends PluginCommand {
+  /// Creates an instance of the test runner command.
   FirebaseTestLabCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -76,11 +78,11 @@ class FirebaseTestLabCommand extends PluginCommand {
       'activate-service-account',
       '--key-file=${argResults['service-key']}',
     ]);
-    int exitCode = await processRunner.runAndStream('gcloud', <String>[
+    final int exitCode = await processRunner.runAndStream('gcloud', <String>[
       'config',
       'set',
       'project',
-      argResults['project'],
+      argResults['project'] as String,
     ]);
     if (exitCode == 0) {
       _print('\nFirebase project configured.');
@@ -93,8 +95,7 @@ class FirebaseTestLabCommand extends PluginCommand {
   }
 
   @override
-  Future<Null> run() async {
-    checkSharding();
+  Future<void> run() async {
     final Stream<Directory> packagesWithTests = getPackages().where(
         (Directory d) =>
             isFlutterPackage(d, fileSystem) &&
@@ -107,7 +108,7 @@ class FirebaseTestLabCommand extends PluginCommand {
     final List<String> missingFlutterBuild = <String>[];
     int resultsCounter =
         0; // We use a unique GCS bucket for each Firebase Test Lab run
-    await for (Directory package in packagesWithTests) {
+    await for (final Directory package in packagesWithTests) {
       // See https://github.com/flutter/flutter/issues/38983
 
       final Directory exampleDirectory =
@@ -119,7 +120,7 @@ class FirebaseTestLabCommand extends PluginCommand {
       final Directory androidDirectory =
           fileSystem.directory(p.join(exampleDirectory.path, 'android'));
 
-      final String enableExperiment = argResults[kEnableExperiment];
+      final String enableExperiment = argResults[kEnableExperiment] as String;
       final String encodedEnableExperiment =
           Uri.encodeComponent('--enable-experiment=$enableExperiment');
 
@@ -166,16 +167,18 @@ class FirebaseTestLabCommand extends PluginCommand {
       // Look for tests recursively in folders that start with 'test' and that
       // live in the root or example folders.
       bool isTestDir(FileSystemEntity dir) {
-        return p.basename(dir.path).startsWith('test') ||
-            p.basename(dir.path) == 'integration_test';
+        return dir is Directory &&
+            (p.basename(dir.path).startsWith('test') ||
+                p.basename(dir.path) == 'integration_test');
       }
 
-      final List<FileSystemEntity> testDirs =
-          package.listSync().where(isTestDir).toList();
+      final List<Directory> testDirs =
+          package.listSync().where(isTestDir).cast<Directory>().toList();
       final Directory example =
           fileSystem.directory(p.join(package.path, 'example'));
-      testDirs.addAll(example.listSync().where(isTestDir).toList());
-      for (Directory testDir in testDirs) {
+      testDirs.addAll(
+          example.listSync().where(isTestDir).cast<Directory>().toList());
+      for (final Directory testDir in testDirs) {
         bool isE2ETest(FileSystemEntity file) {
           return file.path.endsWith('_e2e.dart') ||
               (file.parent.basename == 'integration_test' &&
@@ -186,7 +189,7 @@ class FirebaseTestLabCommand extends PluginCommand {
             .listSync(recursive: true, followLinks: true)
             .where(isE2ETest)
             .toList();
-        for (FileSystemEntity test in testFiles) {
+        for (final FileSystemEntity test in testFiles) {
           exitCode = await processRunner.runAndStream(
               p.join(androidDirectory.path, _gradleWrapper),
               <String>[
@@ -205,7 +208,7 @@ class FirebaseTestLabCommand extends PluginCommand {
             continue;
           }
           final String buildId = io.Platform.environment['CIRRUS_BUILD_ID'];
-          final String testRunId = argResults['test-run-id'];
+          final String testRunId = argResults['test-run-id'] as String;
           final String resultsDir =
               'plugins_android_test/$packageName/$buildId/$testRunId/${resultsCounter++}/';
           final List<String> args = <String>[
@@ -222,9 +225,9 @@ class FirebaseTestLabCommand extends PluginCommand {
             '--timeout',
             '5m',
             '--results-bucket=${argResults['results-bucket']}',
-            '--results-dir=${resultsDir}',
+            '--results-dir=$resultsDir',
           ];
-          for (String device in argResults['device']) {
+          for (final String device in argResults['device'] as List<String>) {
             args.addAll(<String>['--device', device]);
           }
           exitCode = await processRunner.runAndStream('gcloud', args,
@@ -243,14 +246,14 @@ class FirebaseTestLabCommand extends PluginCommand {
       _print(
           'The instrumentation tests for the following packages are failing (see above for'
           'details):');
-      for (String package in failingPackages) {
+      for (final String package in failingPackages) {
         _print(' * $package');
       }
     }
     if (missingFlutterBuild.isNotEmpty) {
       _print('Run "pub global run flutter_plugin_tools build-examples --apk" on'
           'the following packages before executing tests again:');
-      for (String package in missingFlutterBuild) {
+      for (final String package in missingFlutterBuild) {
         _print(' * $package');
       }
     }
diff --git a/script/tool/lib/src/format_command.dart b/script/tool/lib/src/format_command.dart
index d849dc9aa9d2..19b6004d2446 100644
--- a/script/tool/lib/src/format_command.dart
+++ b/script/tool/lib/src/format_command.dart
@@ -16,7 +16,9 @@ import 'common.dart';
 const String _googleFormatterUrl =
     'https://github.com/google/google-java-format/releases/download/google-java-format-1.3/google-java-format-1.3-all-deps.jar';
 
+/// A command to format all package code.
 class FormatCommand extends PluginCommand {
+  /// Creates an instance of the format command.
   FormatCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -38,15 +40,14 @@ class FormatCommand extends PluginCommand {
       'your path.';
 
   @override
-  Future<Null> run() async {
-    checkSharding();
+  Future<void> run() async {
     final String googleFormatterPath = await _getGoogleFormatterPath();
 
     await _formatDart();
     await _formatJava(googleFormatterPath);
     await _formatCppAndObjectiveC();
 
-    if (argResults['fail-on-change']) {
+    if (argResults['fail-on-change'] == true) {
       final bool modified = await _didModifyAnything();
       if (modified) {
         throw ToolExit(1);
@@ -61,15 +62,14 @@ class FormatCommand extends PluginCommand {
 
     print('\n\n');
 
-    if (modifiedFiles.stdout.isEmpty) {
+    final String stdout = modifiedFiles.stdout as String;
+    if (stdout.isEmpty) {
       print('All files formatted correctly.');
       return false;
     }
 
     print('These files are not formatted correctly (see diff below):');
-    LineSplitter.split(modifiedFiles.stdout)
-        .map((String line) => '  $line')
-        .forEach(print);
+    LineSplitter.split(stdout).map((String line) => '  $line').forEach(print);
 
     print('\nTo fix run "pub global activate flutter_plugin_tools && '
         'pub global run flutter_plugin_tools format" or copy-paste '
@@ -83,33 +83,34 @@ class FormatCommand extends PluginCommand {
     return true;
   }
 
-  Future<Null> _formatCppAndObjectiveC() async {
+  Future<void> _formatCppAndObjectiveC() async {
     print('Formatting all .cc, .cpp, .mm, .m, and .h files...');
-    final Iterable<String> allFiles = <String>[]
-      ..addAll(await _getFilesWithExtension('.h'))
-      ..addAll(await _getFilesWithExtension('.m'))
-      ..addAll(await _getFilesWithExtension('.mm'))
-      ..addAll(await _getFilesWithExtension('.cc'))
-      ..addAll(await _getFilesWithExtension('.cpp'));
+    final Iterable<String> allFiles = <String>[
+      ...await _getFilesWithExtension('.h'),
+      ...await _getFilesWithExtension('.m'),
+      ...await _getFilesWithExtension('.mm'),
+      ...await _getFilesWithExtension('.cc'),
+      ...await _getFilesWithExtension('.cpp'),
+    ];
     // Split this into multiple invocations to avoid a
     // 'ProcessException: Argument list too long'.
     final Iterable<List<String>> batches = partition(allFiles, 100);
-    for (List<String> batch in batches) {
-      await processRunner.runAndStream(argResults['clang-format'],
-          <String>['-i', '--style=Google']..addAll(batch),
+    for (final List<String> batch in batches) {
+      await processRunner.runAndStream(argResults['clang-format'] as String,
+          <String>['-i', '--style=Google', ...batch],
           workingDir: packagesDir, exitOnError: true);
     }
   }
 
-  Future<Null> _formatJava(String googleFormatterPath) async {
+  Future<void> _formatJava(String googleFormatterPath) async {
     print('Formatting all .java files...');
     final Iterable<String> javaFiles = await _getFilesWithExtension('.java');
     await processRunner.runAndStream('java',
-        <String>['-jar', googleFormatterPath, '--replace']..addAll(javaFiles),
+        <String>['-jar', googleFormatterPath, '--replace', ...javaFiles],
         workingDir: packagesDir, exitOnError: true);
   }
 
-  Future<Null> _formatDart() async {
+  Future<void> _formatDart() async {
     // This actually should be fine for non-Flutter Dart projects, no need to
     // specifically shell out to dartfmt -w in that case.
     print('Formatting all .dart files...');
@@ -119,7 +120,7 @@ class FormatCommand extends PluginCommand {
           'No .dart files to format. If you set the `--exclude` flag, most likey they were skipped');
     } else {
       await processRunner.runAndStream(
-          'flutter', <String>['format']..addAll(dartFiles),
+          'flutter', <String>['format', ...dartFiles],
           workingDir: packagesDir, exitOnError: true);
     }
   }
diff --git a/script/tool/lib/src/java_test_command.dart b/script/tool/lib/src/java_test_command.dart
index 4b6a561b9e6d..5df97627cecd 100644
--- a/script/tool/lib/src/java_test_command.dart
+++ b/script/tool/lib/src/java_test_command.dart
@@ -9,7 +9,9 @@ import 'package:path/path.dart' as p;
 
 import 'common.dart';
 
+/// A command to run the Java tests of Android plugins.
 class JavaTestCommand extends PluginCommand {
+  /// Creates an instance of the test runner.
   JavaTestCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -27,8 +29,7 @@ class JavaTestCommand extends PluginCommand {
   static const String _gradleWrapper = 'gradlew';
 
   @override
-  Future<Null> run() async {
-    checkSharding();
+  Future<void> run() async {
     final Stream<Directory> examplesWithTests = getExamples().where(
         (Directory d) =>
             isFlutterPackage(d, fileSystem) &&
@@ -41,7 +42,7 @@ class JavaTestCommand extends PluginCommand {
 
     final List<String> failingPackages = <String>[];
     final List<String> missingFlutterBuild = <String>[];
-    await for (Directory example in examplesWithTests) {
+    await for (final Directory example in examplesWithTests) {
       final String packageName =
           p.relative(example.path, from: packagesDir.path);
       print('\nRUNNING JAVA TESTS for $packageName');
@@ -71,14 +72,14 @@ class JavaTestCommand extends PluginCommand {
       print(
           'The Java tests for the following packages are failing (see above for'
           'details):');
-      for (String package in failingPackages) {
+      for (final String package in failingPackages) {
         print(' * $package');
       }
     }
     if (missingFlutterBuild.isNotEmpty) {
       print('Run "pub global run flutter_plugin_tools build-examples --apk" on'
           'the following packages before executing tests again:');
-      for (String package in missingFlutterBuild) {
+      for (final String package in missingFlutterBuild) {
         print(' * $package');
       }
     }
diff --git a/script/tool/lib/src/license_check_command.dart b/script/tool/lib/src/license_check_command.dart
index 4f78e4e96639..adb2f9315298 100644
--- a/script/tool/lib/src/license_check_command.dart
+++ b/script/tool/lib/src/license_check_command.dart
@@ -62,8 +62,8 @@ final List<RegExp> _thirdPartyLicenseBlockRegexes = <RegExp>[
 // Slight variants are not accepted because they may prevent consolidation in
 // tools that assemble all licenses used in distributed applications.
 // standardized.
-final String _fullBsdLicenseText =
-    '''Copyright 2013 The Flutter Authors. All rights reserved.
+const String _fullBsdLicenseText = '''
+Copyright 2013 The Flutter Authors. All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modification,
 are permitted provided that the following conditions are met:
@@ -110,7 +110,7 @@ class LicenseCheckCommand extends PluginCommand {
       'Ensures that all code files have copyright/license blocks.';
 
   @override
-  Future<Null> run() async {
+  Future<void> run() async {
     final Iterable<File> codeFiles = (await _getAllFiles()).where((File file) =>
         _codeFileExtensions.contains(p.extension(file.path)) &&
         !_shouldIgnoreFile(file));
@@ -160,7 +160,7 @@ class LicenseCheckCommand extends PluginCommand {
 
       if (_isThirdParty(file)) {
         if (!_thirdPartyLicenseBlockRegexes
-            .any((regex) => regex.hasMatch(content))) {
+            .any((RegExp regex) => regex.hasMatch(content))) {
           unrecognizedThirdPartyFiles.add(file);
         }
       } else {
@@ -175,7 +175,8 @@ class LicenseCheckCommand extends PluginCommand {
     _print('\n');
 
     // Sort by path for more usable output.
-    final pathCompare = (File a, File b) => a.path.compareTo(b.path);
+    final int Function(File, File) pathCompare =
+        (File a, File b) => a.path.compareTo(b.path);
     incorrectFirstPartyFiles.sort(pathCompare);
     unrecognizedThirdPartyFiles.sort(pathCompare);
 
@@ -200,7 +201,7 @@ class LicenseCheckCommand extends PluginCommand {
           'the new third-party license block.\n');
     }
 
-    bool succeeded =
+    final bool succeeded =
         incorrectFirstPartyFiles.isEmpty && unrecognizedThirdPartyFiles.isEmpty;
     if (succeeded) {
       _print('All source files passed validation!');
@@ -230,7 +231,7 @@ class LicenseCheckCommand extends PluginCommand {
           'Please ensure that they use the exact format used in this repository".\n');
     }
 
-    bool succeeded = incorrectLicenseFiles.isEmpty;
+    final bool succeeded = incorrectLicenseFiles.isEmpty;
     if (succeeded) {
       _print('All LICENSE files passed validation!');
     }
diff --git a/script/tool/lib/src/lint_podspecs_command.dart b/script/tool/lib/src/lint_podspecs_command.dart
index 3261072d71a1..1fe6b71cf11b 100644
--- a/script/tool/lib/src/lint_podspecs_command.dart
+++ b/script/tool/lib/src/lint_podspecs_command.dart
@@ -12,19 +12,19 @@ import 'package:platform/platform.dart';
 
 import 'common.dart';
 
-typedef void Print(Object object);
-
 /// Lint the CocoaPod podspecs and run unit tests.
 ///
 /// See https://guides.cocoapods.org/terminal/commands.html#pod_lib_lint.
 class LintPodspecsCommand extends PluginCommand {
+  /// Creates an instance of the linter command.
   LintPodspecsCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
     ProcessRunner processRunner = const ProcessRunner(),
-    this.platform = const LocalPlatform(),
+    Platform platform = const LocalPlatform(),
     Print print = print,
-  })  : _print = print,
+  })  : _platform = platform,
+        _print = print,
         super(packagesDir, fileSystem, processRunner: processRunner) {
     argParser.addMultiOption('skip',
         help:
@@ -47,26 +47,24 @@ class LintPodspecsCommand extends PluginCommand {
       'Runs "pod lib lint" on all iOS and macOS plugin podspecs.\n\n'
       'This command requires "pod" and "flutter" to be in your path. Runs on macOS only.';
 
-  final Platform platform;
+  final Platform _platform;
 
   final Print _print;
 
   @override
-  Future<Null> run() async {
-    if (!platform.isMacOS) {
+  Future<void> run() async {
+    if (!_platform.isMacOS) {
       _print('Detected platform is not macOS, skipping podspec lint');
       return;
     }
 
-    checkSharding();
-
     await processRunner.runAndExitOnError('which', <String>['pod'],
         workingDir: packagesDir);
 
     _print('Starting podspec lint test');
 
     final List<String> failingPlugins = <String>[];
-    for (File podspec in await _podspecsToLint()) {
+    for (final File podspec in await _podspecsToLint()) {
       if (!await _lintPodspec(podspec)) {
         failingPlugins.add(p.basenameWithoutExtension(podspec.path));
       }
@@ -75,9 +73,9 @@ class LintPodspecsCommand extends PluginCommand {
     _print('\n\n');
     if (failingPlugins.isNotEmpty) {
       _print('The following plugins have podspec errors (see above):');
-      failingPlugins.forEach((String plugin) {
+      for (final String plugin in failingPlugins) {
         _print(' * $plugin');
-      });
+      }
       throw ToolExit(1);
     }
   }
@@ -86,7 +84,8 @@ class LintPodspecsCommand extends PluginCommand {
     final List<File> podspecs = await getFiles().where((File entity) {
       final String filePath = entity.path;
       return p.extension(filePath) == '.podspec' &&
-          !argResults['skip'].contains(p.basenameWithoutExtension(filePath));
+          !(argResults['skip'] as List<String>)
+              .contains(p.basenameWithoutExtension(filePath));
     }).toList();
 
     podspecs.sort(
@@ -102,12 +101,14 @@ class LintPodspecsCommand extends PluginCommand {
     _print('Linting $podspecBasename');
 
     // Lint plugin as framework (use_frameworks!).
-    final ProcessResult frameworkResult = await _runPodLint(podspecPath, libraryLint: true);
+    final ProcessResult frameworkResult =
+        await _runPodLint(podspecPath, libraryLint: true);
     _print(frameworkResult.stdout);
     _print(frameworkResult.stderr);
 
     // Lint plugin as library.
-    final ProcessResult libraryResult = await _runPodLint(podspecPath, libraryLint: false);
+    final ProcessResult libraryResult =
+        await _runPodLint(podspecPath, libraryLint: false);
     _print(libraryResult.stdout);
     _print(libraryResult.stderr);
 
@@ -116,7 +117,7 @@ class LintPodspecsCommand extends PluginCommand {
 
   Future<ProcessResult> _runPodLint(String podspecPath,
       {bool libraryLint}) async {
-    final bool allowWarnings = argResults['ignore-warnings']
+    final bool allowWarnings = (argResults['ignore-warnings'] as List<String>)
         .contains(p.basenameWithoutExtension(podspecPath));
     final List<String> arguments = <String>[
       'lib',
diff --git a/script/tool/lib/src/list_command.dart b/script/tool/lib/src/list_command.dart
index 3571786ab7f8..49302a91ad27 100644
--- a/script/tool/lib/src/list_command.dart
+++ b/script/tool/lib/src/list_command.dart
@@ -8,7 +8,10 @@ import 'package:file/file.dart';
 
 import 'common.dart';
 
+/// A command to list different types of repository content.
 class ListCommand extends PluginCommand {
+  /// Creates an instance of the list command, whose behavior depends on the
+  /// 'type' argument it provides.
   ListCommand(Directory packagesDir, FileSystem fileSystem)
       : super(packagesDir, fileSystem) {
     argParser.addOption(
@@ -32,26 +35,25 @@ class ListCommand extends PluginCommand {
   final String description = 'Lists packages or files';
 
   @override
-  Future<Null> run() async {
-    checkSharding();
-    switch (argResults[_type]) {
+  Future<void> run() async {
+    switch (argResults[_type] as String) {
       case _plugin:
-        await for (Directory package in getPlugins()) {
+        await for (final Directory package in getPlugins()) {
           print(package.path);
         }
         break;
       case _example:
-        await for (Directory package in getExamples()) {
+        await for (final Directory package in getExamples()) {
           print(package.path);
         }
         break;
       case _package:
-        await for (Directory package in getPackages()) {
+        await for (final Directory package in getPackages()) {
           print(package.path);
         }
         break;
       case _file:
-        await for (File file in getFiles()) {
+        await for (final File file in getFiles()) {
           print(file.path);
         }
         break;
diff --git a/script/tool/lib/src/main.dart b/script/tool/lib/src/main.dart
index 2e29aac1e784..6fba3b34b955 100644
--- a/script/tool/lib/src/main.dart
+++ b/script/tool/lib/src/main.dart
@@ -27,7 +27,7 @@ import 'version_check_command.dart';
 import 'xctest_command.dart';
 
 void main(List<String> args) {
-  final FileSystem fileSystem = const LocalFileSystem();
+  const FileSystem fileSystem = LocalFileSystem();
 
   Directory packagesDir = fileSystem
       .directory(p.join(fileSystem.currentDirectory.path, 'packages'));
@@ -41,7 +41,7 @@ void main(List<String> args) {
     }
   }
 
-  final CommandRunner<Null> commandRunner = CommandRunner<Null>(
+  final CommandRunner<void> commandRunner = CommandRunner<void>(
       'pub global run flutter_plugin_tools',
       'Productivity utils for hosting multiple plugins within one repository.')
     ..addCommand(AnalyzeCommand(packagesDir, fileSystem))
@@ -61,7 +61,7 @@ void main(List<String> args) {
     ..addCommand(XCTestCommand(packagesDir, fileSystem));
 
   commandRunner.run(args).catchError((Object e) {
-    final ToolExit toolExit = e;
+    final ToolExit toolExit = e as ToolExit;
     io.exit(toolExit.exitCode);
   }, test: (Object e) => e is ToolExit);
 }
diff --git a/script/tool/lib/src/publish_check_command.dart b/script/tool/lib/src/publish_check_command.dart
index fb57dfcd6dc9..07bf0aa86673 100644
--- a/script/tool/lib/src/publish_check_command.dart
+++ b/script/tool/lib/src/publish_check_command.dart
@@ -11,7 +11,9 @@ import 'package:pubspec_parse/pubspec_parse.dart';
 
 import 'common.dart';
 
+/// A command to check that packages are publishable via 'dart publish'.
 class PublishCheckCommand extends PluginCommand {
+  /// Creates an instance of the publish command.
   PublishCheckCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -26,12 +28,13 @@ class PublishCheckCommand extends PluginCommand {
       'Checks to make sure that a plugin *could* be published.';
 
   @override
-  Future<Null> run() async {
-    checkSharding();
+  Future<void> run() async {
     final List<Directory> failedPackages = <Directory>[];
 
-    await for (Directory plugin in getPlugins()) {
-      if (!(await passesPublishCheck(plugin))) failedPackages.add(plugin);
+    await for (final Directory plugin in getPlugins()) {
+      if (!(await _passesPublishCheck(plugin))) {
+        failedPackages.add(plugin);
+      }
     }
 
     if (failedPackages.isNotEmpty) {
@@ -51,7 +54,7 @@ class PublishCheckCommand extends PluginCommand {
     print(passedMessage);
   }
 
-  Pubspec tryParsePubspec(Directory package) {
+  Pubspec _tryParsePubspec(Directory package) {
     final File pubspecFile = package.childFile('pubspec.yaml');
 
     try {
@@ -64,7 +67,7 @@ class PublishCheckCommand extends PluginCommand {
     }
   }
 
-  Future<bool> hasValidPublishCheckRun(Directory package) async {
+  Future<bool> _hasValidPublishCheckRun(Directory package) async {
     final io.Process process = await processRunner.start(
       'flutter',
       <String>['pub', 'publish', '--', '--dry-run'],
@@ -91,7 +94,9 @@ class PublishCheckCommand extends PluginCommand {
       onDone: () => stdInCompleter.complete(),
     );
 
-    if (await process.exitCode == 0) return true;
+    if (await process.exitCode == 0) {
+      return true;
+    }
 
     await stdOutCompleter.future;
     await stdInCompleter.future;
@@ -102,11 +107,11 @@ class PublishCheckCommand extends PluginCommand {
             'Packages with an SDK constraint on a pre-release of the Dart SDK should themselves be published as a pre-release version.');
   }
 
-  Future<bool> passesPublishCheck(Directory package) async {
+  Future<bool> _passesPublishCheck(Directory package) async {
     final String packageName = package.basename;
     print('Checking that $packageName can be published.');
 
-    final Pubspec pubspec = tryParsePubspec(package);
+    final Pubspec pubspec = _tryParsePubspec(package);
     if (pubspec == null) {
       return false;
     } else if (pubspec.publishTo == 'none') {
@@ -114,8 +119,8 @@ class PublishCheckCommand extends PluginCommand {
       return true;
     }
 
-    if (await hasValidPublishCheckRun(package)) {
-      print("Package $packageName is able to be published.");
+    if (await _hasValidPublishCheckRun(package)) {
+      print('Package $packageName is able to be published.');
       return true;
     } else {
       print('Unable to publish $packageName');
diff --git a/script/tool/lib/src/publish_plugin_command.dart b/script/tool/lib/src/publish_plugin_command.dart
index d00400294ab3..0dae3a502be1 100644
--- a/script/tool/lib/src/publish_plugin_command.dart
+++ b/script/tool/lib/src/publish_plugin_command.dart
@@ -26,6 +26,7 @@ import 'common.dart';
 ///
 /// [processRunner], [print], and [stdin] can be overriden for easier testing.
 class PublishPluginCommand extends PluginCommand {
+  /// Creates an instance of the publish command.
   PublishPluginCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -88,9 +89,8 @@ class PublishPluginCommand extends PluginCommand {
   StreamSubscription<String> _stdinSubscription;
 
   @override
-  Future<Null> run() async {
-    checkSharding();
-    final String package = argResults[_packageOption];
+  Future<void> run() async {
+    final String package = argResults[_packageOption] as String;
     if (package == null) {
       _print(
           'Must specify a package to publish. See `plugin_tools help publish-plugin`.');
@@ -103,8 +103,8 @@ class PublishPluginCommand extends PluginCommand {
       throw ToolExit(1);
     }
 
-    final bool shouldPushTag = argResults[_pushTagsOption];
-    final String remote = argResults[_remoteOption];
+    final bool shouldPushTag = argResults[_pushTagsOption] == true;
+    final String remote = argResults[_remoteOption] as String;
     String remoteUrl;
     if (shouldPushTag) {
       remoteUrl = await _verifyRemote(remote);
@@ -173,7 +173,7 @@ class PublishPluginCommand extends PluginCommand {
         ],
         workingDir: packageDir);
 
-    final String statusOutput = statusResult.stdout;
+    final String statusOutput = statusResult.stdout as String;
     if (statusOutput.isNotEmpty) {
       _print(
           "There are files in the package directory that haven't been saved in git. Refusing to publish these files:\n\n"
@@ -187,11 +187,12 @@ class PublishPluginCommand extends PluginCommand {
     final ProcessResult remoteInfo = await processRunner.runAndExitOnError(
         'git', <String>['remote', 'get-url', remote],
         workingDir: packagesDir);
-    return remoteInfo.stdout;
+    return remoteInfo.stdout as String;
   }
 
   Future<void> _publish(Directory packageDir) async {
-    final List<String> publishFlags = argResults[_pubFlagsOption];
+    final List<String> publishFlags =
+        argResults[_pubFlagsOption] as List<String>;
     _print(
         'Running `pub publish ${publishFlags.join(' ')}` in ${packageDir.absolute.path}...\n');
     final Process publish = await processRunner.start(
@@ -216,9 +217,10 @@ class PublishPluginCommand extends PluginCommand {
   String _getTag(Directory packageDir) {
     final File pubspecFile =
         fileSystem.file(p.join(packageDir.path, 'pubspec.yaml'));
-    final YamlMap pubspecYaml = loadYaml(pubspecFile.readAsStringSync());
-    final String name = pubspecYaml['name'];
-    final String version = pubspecYaml['version'];
+    final YamlMap pubspecYaml =
+        loadYaml(pubspecFile.readAsStringSync()) as YamlMap;
+    final String name = pubspecYaml['name'] as String;
+    final String version = pubspecYaml['version'] as String;
     // We should have failed to publish if these were unset.
     assert(name.isNotEmpty && version.isNotEmpty);
     return _tagFormat
diff --git a/script/tool/lib/src/test_command.dart b/script/tool/lib/src/test_command.dart
index 10ded4621ab5..bb4f9c12a77f 100644
--- a/script/tool/lib/src/test_command.dart
+++ b/script/tool/lib/src/test_command.dart
@@ -9,7 +9,9 @@ import 'package:path/path.dart' as p;
 
 import 'common.dart';
 
+/// A command to run Dart unit tests for packages.
 class TestCommand extends PluginCommand {
+  /// Creates an instance of the test command.
   TestCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -30,10 +32,9 @@ class TestCommand extends PluginCommand {
       'This command requires "flutter" to be in your path.';
 
   @override
-  Future<Null> run() async {
-    checkSharding();
+  Future<void> run() async {
     final List<String> failingPackages = <String>[];
-    await for (Directory packageDir in getPackages()) {
+    await for (final Directory packageDir in getPackages()) {
       final String packageName =
           p.relative(packageDir.path, from: packagesDir.path);
       if (!fileSystem.directory(p.join(packageDir.path, 'test')).existsSync()) {
@@ -43,7 +44,7 @@ class TestCommand extends PluginCommand {
 
       print('RUNNING $packageName tests...');
 
-      final String enableExperiment = argResults[kEnableExperiment];
+      final String enableExperiment = argResults[kEnableExperiment] as String;
 
       // `flutter test` automatically gets packages.  `pub run test` does not.  :(
       int exitCode = 0;
@@ -90,9 +91,9 @@ class TestCommand extends PluginCommand {
     print('\n\n');
     if (failingPackages.isNotEmpty) {
       print('Tests for the following packages are failing (see above):');
-      failingPackages.forEach((String package) {
+      for (final String package in failingPackages) {
         print(' * $package');
-      });
+      }
       throw ToolExit(1);
     }
 
diff --git a/script/tool/lib/src/version_check_command.dart b/script/tool/lib/src/version_check_command.dart
index fb939a71e38a..086fa548880f 100644
--- a/script/tool/lib/src/version_check_command.dart
+++ b/script/tool/lib/src/version_check_command.dart
@@ -15,47 +15,32 @@ import 'common.dart';
 
 const String _kBaseSha = 'base-sha';
 
+/// Categories of version change types.
 enum NextVersionType {
+  /// A breaking change.
   BREAKING_MAJOR,
-  MAJOR_NULLSAFETY_PRE_RELEASE,
-  MINOR_NULLSAFETY_PRE_RELEASE,
+
+  /// A minor change (e.g., added feature).
   MINOR,
+
+  /// A bugfix change.
   PATCH,
-  RELEASE,
-}
 
-Version getNextNullSafetyPreRelease(Version current, Version next) {
-  String nextNullsafetyPrerelease = 'nullsafety';
-  if (current.isPreRelease &&
-      current.preRelease.first is String &&
-      current.preRelease.first == 'nullsafety') {
-    if (current.preRelease.length == 1) {
-      nextNullsafetyPrerelease = 'nullsafety.1';
-    } else if (current.preRelease.length == 2 &&
-        current.preRelease.last is int) {
-      nextNullsafetyPrerelease = 'nullsafety.${current.preRelease.last + 1}';
-    }
-  }
-  return Version(
-    next.major,
-    next.minor,
-    next.patch,
-    pre: nextNullsafetyPrerelease,
-  );
+  /// The release of an existing prerelease version.
+  RELEASE,
 }
 
+/// Returns the set of allowed next versions, with their change type, for
+/// [masterVersion].
+///
+/// [headVerison] is used to check whether this is a pre-1.0 version bump, as
+/// those have different semver rules.
 @visibleForTesting
 Map<Version, NextVersionType> getAllowedNextVersions(
     Version masterVersion, Version headVersion) {
-  final Version nextNullSafetyMajor =
-      getNextNullSafetyPreRelease(masterVersion, masterVersion.nextMajor);
-  final Version nextNullSafetyMinor =
-      getNextNullSafetyPreRelease(masterVersion, masterVersion.nextMinor);
   final Map<Version, NextVersionType> allowedNextVersions =
       <Version, NextVersionType>{
     masterVersion.nextMajor: NextVersionType.BREAKING_MAJOR,
-    nextNullSafetyMajor: NextVersionType.MAJOR_NULLSAFETY_PRE_RELEASE,
-    nextNullSafetyMinor: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE,
     masterVersion.nextMinor: NextVersionType.MINOR,
     masterVersion.nextPatch: NextVersionType.PATCH,
   };
@@ -65,7 +50,7 @@ Map<Version, NextVersionType> getAllowedNextVersions(
     if (masterVersion.build.isEmpty) {
       nextBuildNumber = 1;
     } else {
-      final int currentBuildNumber = masterVersion.build.first;
+      final int currentBuildNumber = masterVersion.build.first as int;
       nextBuildNumber = currentBuildNumber + 1;
     }
     final Version preReleaseVersion = Version(
@@ -80,21 +65,13 @@ Map<Version, NextVersionType> getAllowedNextVersions(
         NextVersionType.BREAKING_MAJOR;
     allowedNextVersions[masterVersion.nextPatch] = NextVersionType.MINOR;
     allowedNextVersions[preReleaseVersion] = NextVersionType.PATCH;
-
-    final Version nextNullSafetyMajor =
-        getNextNullSafetyPreRelease(masterVersion, masterVersion.nextMinor);
-    final Version nextNullSafetyMinor =
-        getNextNullSafetyPreRelease(masterVersion, masterVersion.nextPatch);
-
-    allowedNextVersions[nextNullSafetyMajor] =
-        NextVersionType.MAJOR_NULLSAFETY_PRE_RELEASE;
-    allowedNextVersions[nextNullSafetyMinor] =
-        NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE;
   }
   return allowedNextVersions;
 }
 
+/// A command to validate version changes to packages.
 class VersionCheckCommand extends PluginCommand {
+  /// Creates an instance of the version check command.
   VersionCheckCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -113,14 +90,13 @@ class VersionCheckCommand extends PluginCommand {
       'This command requires "pub" and "flutter" to be in your path.';
 
   @override
-  Future<Null> run() async {
-    checkSharding();
+  Future<void> run() async {
     final GitVersionFinder gitVersionFinder = await retrieveVersionFinder();
 
     final List<String> changedPubspecs =
         await gitVersionFinder.getChangedPubSpecs();
 
-    final String baseSha = argResults[_kBaseSha];
+    final String baseSha = argResults[_kBaseSha] as String;
     for (final String pubspecPath in changedPubspecs) {
       try {
         final File pubspecFile = fileSystem.file(pubspecPath);
@@ -150,7 +126,8 @@ class VersionCheckCommand extends PluginCommand {
           printErrorAndExit(errorMessage: error);
         }
 
-        bool isPlatformInterface = pubspec.name.endsWith("_platform_interface");
+        final bool isPlatformInterface =
+            pubspec.name.endsWith('_platform_interface');
         if (isPlatformInterface &&
             allowedNextVersions[headVersion] ==
                 NextVersionType.BREAKING_MAJOR) {
@@ -164,7 +141,7 @@ class VersionCheckCommand extends PluginCommand {
       }
     }
 
-    await for (Directory plugin in getPlugins()) {
+    await for (final Directory plugin in getPlugins()) {
       await _checkVersionsMatch(plugin);
     }
 
@@ -180,7 +157,7 @@ class VersionCheckCommand extends PluginCommand {
 
     final Pubspec pubspec = _tryParsePubspec(plugin);
     if (pubspec == null) {
-      final String error = 'Cannot parse version from pubspec.yaml';
+      const String error = 'Cannot parse version from pubspec.yaml';
       printErrorAndExit(errorMessage: error);
     }
     final Version fromPubspec = pubspec.version;
@@ -189,16 +166,16 @@ class VersionCheckCommand extends PluginCommand {
     final File changelog = plugin.childFile('CHANGELOG.md');
     final List<String> lines = changelog.readAsLinesSync();
     String firstLineWithText;
-    final Iterator iterator = lines.iterator;
+    final Iterator<String> iterator = lines.iterator;
     while (iterator.moveNext()) {
-      if ((iterator.current as String).trim().isNotEmpty) {
+      if (iterator.current.trim().isNotEmpty) {
         firstLineWithText = iterator.current;
         break;
       }
     }
     // Remove all leading mark down syntax from the version line.
     final String versionString = firstLineWithText.split(' ').last;
-    Version fromChangeLog = Version.parse(versionString);
+    final Version fromChangeLog = Version.parse(versionString);
     if (fromChangeLog == null) {
       final String error =
           'Cannot find version on the first line of ${plugin.path}/CHANGELOG.md';
@@ -213,14 +190,14 @@ The first version listed in CHANGELOG.md is $fromChangeLog.
 ''';
       printErrorAndExit(errorMessage: error);
     }
-    print('${packageName} passed version check');
+    print('$packageName passed version check');
   }
 
   Pubspec _tryParsePubspec(Directory package) {
     final File pubspecFile = package.childFile('pubspec.yaml');
 
     try {
-      Pubspec pubspec = Pubspec.parse(pubspecFile.readAsStringSync());
+      final Pubspec pubspec = Pubspec.parse(pubspecFile.readAsStringSync());
       if (pubspec == null) {
         final String error =
             'Failed to parse `pubspec.yaml` at ${pubspecFile.path}';
diff --git a/script/tool/lib/src/xctest_command.dart b/script/tool/lib/src/xctest_command.dart
index 41974713f99b..64f85577dbce 100644
--- a/script/tool/lib/src/xctest_command.dart
+++ b/script/tool/lib/src/xctest_command.dart
@@ -22,6 +22,7 @@ const String _kFoundNoSimulatorsMessage =
 /// The tests target have to be added to the xcode project of the example app. Usually at "example/ios/Runner.xcworkspace".
 /// The static analyzer is also run.
 class XCTestCommand extends PluginCommand {
+  /// Creates an instance of the test command.
   XCTestCommand(
     Directory packagesDir,
     FileSystem fileSystem, {
@@ -46,10 +47,10 @@ class XCTestCommand extends PluginCommand {
       'This command requires "flutter" and "xcrun" to be in your path.';
 
   @override
-  Future<Null> run() async {
-    String destination = argResults[_kiOSDestination];
+  Future<void> run() async {
+    String destination = argResults[_kiOSDestination] as String;
     if (destination == null) {
-      String simulatorId = await _findAvailableIphoneSimulator();
+      final String simulatorId = await _findAvailableIphoneSimulator();
       if (simulatorId == null) {
         print(_kFoundNoSimulatorsMessage);
         throw ToolExit(1);
@@ -57,12 +58,10 @@ class XCTestCommand extends PluginCommand {
       destination = 'id=$simulatorId';
     }
 
-    checkSharding();
+    final List<String> skipped = argResults[_kSkip] as List<String>;
 
-    final List<String> skipped = argResults[_kSkip];
-
-    List<String> failingPackages = <String>[];
-    await for (Directory plugin in getPlugins()) {
+    final List<String> failingPackages = <String>[];
+    await for (final Directory plugin in getPlugins()) {
       // Start running for package.
       final String packageName =
           p.relative(plugin.path, from: packagesDir.path);
@@ -77,7 +76,7 @@ class XCTestCommand extends PluginCommand {
         print('\n\n');
         continue;
       }
-      for (Directory example in getExamplesForPlugin(plugin)) {
+      for (final Directory example in getExamplesForPlugin(plugin)) {
         // Running tests and static analyzer.
         print('Running tests and analyzer for $packageName ...');
         int exitCode = await _runTests(true, destination, example);
@@ -96,11 +95,11 @@ class XCTestCommand extends PluginCommand {
 
     // Command end, print reports.
     if (failingPackages.isEmpty) {
-      print("All XCTests have passed!");
+      print('All XCTests have passed!');
     } else {
       print(
           'The following packages are failing XCTests (see above for details):');
-      for (String package in failingPackages) {
+      for (final String package in failingPackages) {
         print(' * $package');
       }
       throw ToolExit(1);
@@ -110,8 +109,7 @@ class XCTestCommand extends PluginCommand {
   Future<int> _runTests(bool runTests, String destination, Directory example) {
     final List<String> xctestArgs = <String>[
       _kXcodeBuildCommand,
-      if (runTests)
-        'test',
+      if (runTests) 'test',
       'analyze',
       '-workspace',
       'ios/Runner.xcworkspace',
@@ -128,8 +126,8 @@ class XCTestCommand extends PluginCommand {
     final String completeTestCommand =
         '$_kXCRunCommand ${xctestArgs.join(' ')}';
     print(completeTestCommand);
-    return processRunner
-        .runAndStream(_kXCRunCommand, xctestArgs, workingDir: example, exitOnError: false);
+    return processRunner.runAndStream(_kXCRunCommand, xctestArgs,
+        workingDir: example, exitOnError: false);
   }
 
   Future<String> _findAvailableIphoneSimulator() async {
@@ -151,30 +149,35 @@ class XCTestCommand extends PluginCommand {
       throw ToolExit(1);
     }
     final Map<String, dynamic> simulatorListJson =
-        jsonDecode(findSimulatorsResult.stdout);
-    final List<dynamic> runtimes = simulatorListJson['runtimes'];
-    final Map<String, dynamic> devices = simulatorListJson['devices'];
+        jsonDecode(findSimulatorsResult.stdout as String)
+            as Map<String, dynamic>;
+    final List<Map<String, dynamic>> runtimes =
+        (simulatorListJson['runtimes'] as List<dynamic>)
+            .cast<Map<String, dynamic>>();
+    final Map<String, dynamic> devices =
+        simulatorListJson['devices'] as Map<String, dynamic>;
     if (runtimes.isEmpty || devices.isEmpty) {
       return null;
     }
     String id;
     // Looking for runtimes, trying to find one with highest OS version.
-    for (Map<String, dynamic> runtimeMap in runtimes.reversed) {
-      if (!runtimeMap['name'].contains('iOS')) {
+    for (final Map<String, dynamic> runtimeMap in runtimes.reversed) {
+      if (!(runtimeMap['name'] as String).contains('iOS')) {
         continue;
       }
-      final String runtimeID = runtimeMap['identifier'];
-      final List<dynamic> devicesForRuntime = devices[runtimeID];
+      final String runtimeID = runtimeMap['identifier'] as String;
+      final List<Map<String, dynamic>> devicesForRuntime =
+          (devices[runtimeID] as List<dynamic>).cast<Map<String, dynamic>>();
       if (devicesForRuntime.isEmpty) {
         continue;
       }
       // Looking for runtimes, trying to find latest version of device.
-      for (Map<String, dynamic> device in devicesForRuntime.reversed) {
+      for (final Map<String, dynamic> device in devicesForRuntime.reversed) {
         if (device['availabilityError'] != null ||
             (device['isAvailable'] as bool == false)) {
           continue;
         }
-        id = device['udid'];
+        id = device['udid'] as String;
         print('device selected: $device');
         return id;
       }
diff --git a/script/tool/test/analyze_command_test.dart b/script/tool/test/analyze_command_test.dart
index 636d4794a484..7b23ea9778e9 100644
--- a/script/tool/test/analyze_command_test.dart
+++ b/script/tool/test/analyze_command_test.dart
@@ -13,7 +13,7 @@ import 'util.dart';
 
 void main() {
   RecordingProcessRunner processRunner;
-  CommandRunner runner;
+  CommandRunner<void> runner;
 
   setUp(() {
     initializeFakePackages();
@@ -22,7 +22,7 @@ void main() {
         mockPackagesDir, mockFileSystem,
         processRunner: processRunner);
 
-    runner = CommandRunner<Null>('analyze_command', 'Test for analyze_command');
+    runner = CommandRunner<void>('analyze_command', 'Test for analyze_command');
     runner.addCommand(analyzeCommand);
   });
 
@@ -31,8 +31,8 @@ void main() {
   });
 
   test('analyzes all packages', () async {
-    final Directory plugin1Dir = await createFakePlugin('a');
-    final Directory plugin2Dir = await createFakePlugin('b');
+    final Directory plugin1Dir = createFakePlugin('a');
+    final Directory plugin2Dir = createFakePlugin('b');
 
     final MockProcess mockProcess = MockProcess();
     mockProcess.exitCodeCompleter.complete(0);
@@ -42,20 +42,22 @@ void main() {
     expect(
         processRunner.recordedCalls,
         orderedEquals(<ProcessCall>[
-          ProcessCall('pub', <String>['global', 'activate', 'tuneup'],
+          ProcessCall('pub', const <String>['global', 'activate', 'tuneup'],
               mockPackagesDir.path),
-          ProcessCall('flutter', <String>['packages', 'get'], plugin1Dir.path),
-          ProcessCall('flutter', <String>['packages', 'get'], plugin2Dir.path),
-          ProcessCall('pub', <String>['global', 'run', 'tuneup', 'check'],
+          ProcessCall(
+              'flutter', const <String>['packages', 'get'], plugin1Dir.path),
+          ProcessCall(
+              'flutter', const <String>['packages', 'get'], plugin2Dir.path),
+          ProcessCall('pub', const <String>['global', 'run', 'tuneup', 'check'],
               plugin1Dir.path),
-          ProcessCall('pub', <String>['global', 'run', 'tuneup', 'check'],
+          ProcessCall('pub', const <String>['global', 'run', 'tuneup', 'check'],
               plugin2Dir.path),
         ]));
   });
 
   group('verifies analysis settings', () {
     test('fails analysis_options.yaml', () async {
-      await createFakePlugin('foo', withExtraFiles: <List<String>>[
+      createFakePlugin('foo', withExtraFiles: <List<String>>[
         <String>['analysis_options.yaml']
       ]);
 
@@ -64,7 +66,7 @@ void main() {
     });
 
     test('fails .analysis_options', () async {
-      await createFakePlugin('foo', withExtraFiles: <List<String>>[
+      createFakePlugin('foo', withExtraFiles: <List<String>>[
         <String>['.analysis_options']
       ]);
 
@@ -74,7 +76,7 @@ void main() {
 
     test('takes an allow list', () async {
       final Directory pluginDir =
-          await createFakePlugin('foo', withExtraFiles: <List<String>>[
+          createFakePlugin('foo', withExtraFiles: <List<String>>[
         <String>['analysis_options.yaml']
       ]);
 
@@ -86,17 +88,20 @@ void main() {
       expect(
           processRunner.recordedCalls,
           orderedEquals(<ProcessCall>[
-            ProcessCall('pub', <String>['global', 'activate', 'tuneup'],
+            ProcessCall('pub', const <String>['global', 'activate', 'tuneup'],
                 mockPackagesDir.path),
-            ProcessCall('flutter', <String>['packages', 'get'], pluginDir.path),
-            ProcessCall('pub', <String>['global', 'run', 'tuneup', 'check'],
+            ProcessCall(
+                'flutter', const <String>['packages', 'get'], pluginDir.path),
+            ProcessCall(
+                'pub',
+                const <String>['global', 'run', 'tuneup', 'check'],
                 pluginDir.path),
           ]));
     });
 
     // See: https://github.com/flutter/flutter/issues/78994
     test('takes an empty allow list', () async {
-      await createFakePlugin('foo', withExtraFiles: <List<String>>[
+      createFakePlugin('foo', withExtraFiles: <List<String>>[
         <String>['analysis_options.yaml']
       ]);
 
diff --git a/script/tool/test/build_examples_command_test.dart b/script/tool/test/build_examples_command_test.dart
index f9ee6dcf25db..40da27d44923 100644
--- a/script/tool/test/build_examples_command_test.dart
+++ b/script/tool/test/build_examples_command_test.dart
@@ -13,10 +13,10 @@ import 'util.dart';
 
 void main() {
   group('test build_example_command', () {
-    CommandRunner<Null> runner;
+    CommandRunner<void> runner;
     RecordingProcessRunner processRunner;
     final String flutterCommand =
-        LocalPlatform().isWindows ? 'flutter.bat' : 'flutter';
+        const LocalPlatform().isWindows ? 'flutter.bat' : 'flutter';
 
     setUp(() {
       initializeFakePackages();
@@ -25,7 +25,7 @@ void main() {
           mockPackagesDir, mockFileSystem,
           processRunner: processRunner);
 
-      runner = CommandRunner<Null>(
+      runner = CommandRunner<void>(
           'build_examples_command', 'Test for build_example_command');
       runner.addCommand(command);
       cleanupPackages();
@@ -102,7 +102,7 @@ void main() {
           orderedEquals(<ProcessCall>[
             ProcessCall(
                 flutterCommand,
-                <String>[
+                const <String>[
                   'build',
                   'ios',
                   '--no-codesign',
@@ -179,7 +179,7 @@ void main() {
       expect(
           processRunner.recordedCalls,
           orderedEquals(<ProcessCall>[
-            ProcessCall(flutterCommand, <String>['build', 'linux'],
+            ProcessCall(flutterCommand, const <String>['build', 'linux'],
                 pluginExampleDirectory.path),
           ]));
       cleanupPackages();
@@ -249,7 +249,7 @@ void main() {
       expect(
           processRunner.recordedCalls,
           orderedEquals(<ProcessCall>[
-            ProcessCall(flutterCommand, <String>['build', 'macos'],
+            ProcessCall(flutterCommand, const <String>['build', 'macos'],
                 pluginExampleDirectory.path),
           ]));
       cleanupPackages();
@@ -318,7 +318,7 @@ void main() {
       expect(
           processRunner.recordedCalls,
           orderedEquals(<ProcessCall>[
-            ProcessCall(flutterCommand, <String>['build', 'web'],
+            ProcessCall(flutterCommand, const <String>['build', 'web'],
                 pluginExampleDirectory.path),
           ]));
       cleanupPackages();
@@ -390,7 +390,7 @@ void main() {
       expect(
           processRunner.recordedCalls,
           orderedEquals(<ProcessCall>[
-            ProcessCall(flutterCommand, <String>['build', 'windows'],
+            ProcessCall(flutterCommand, const <String>['build', 'windows'],
                 pluginExampleDirectory.path),
           ]));
       cleanupPackages();
@@ -466,7 +466,7 @@ void main() {
       expect(
           processRunner.recordedCalls,
           orderedEquals(<ProcessCall>[
-            ProcessCall(flutterCommand, <String>['build', 'apk'],
+            ProcessCall(flutterCommand, const <String>['build', 'apk'],
                 pluginExampleDirectory.path),
           ]));
       cleanupPackages();
@@ -498,7 +498,7 @@ void main() {
           orderedEquals(<ProcessCall>[
             ProcessCall(
                 flutterCommand,
-                <String>['build', 'apk', '--enable-experiment=exp1'],
+                const <String>['build', 'apk', '--enable-experiment=exp1'],
                 pluginExampleDirectory.path),
           ]));
       cleanupPackages();
@@ -528,7 +528,7 @@ void main() {
           orderedEquals(<ProcessCall>[
             ProcessCall(
                 flutterCommand,
-                <String>[
+                const <String>[
                   'build',
                   'ios',
                   '--no-codesign',
diff --git a/script/tool/test/common_test.dart b/script/tool/test/common_test.dart
index 6f51ade64e83..57bc1e20f915 100644
--- a/script/tool/test/common_test.dart
+++ b/script/tool/test/common_test.dart
@@ -15,7 +15,7 @@ import 'util.dart';
 
 void main() {
   RecordingProcessRunner processRunner;
-  CommandRunner runner;
+  CommandRunner<void> runner;
   List<String> plugins;
   List<List<String>> gitDirCommands;
   String gitDiffResponse;
@@ -25,16 +25,17 @@ void main() {
     gitDiffResponse = '';
     final MockGitDir gitDir = MockGitDir();
     when(gitDir.runCommand(any)).thenAnswer((Invocation invocation) {
-      gitDirCommands.add(invocation.positionalArguments[0]);
+      gitDirCommands.add(invocation.positionalArguments[0] as List<String>);
       final MockProcessResult mockProcessResult = MockProcessResult();
       if (invocation.positionalArguments[0][0] == 'diff') {
-        when<String>(mockProcessResult.stdout).thenReturn(gitDiffResponse);
+        when<String>(mockProcessResult.stdout as String)
+            .thenReturn(gitDiffResponse);
       }
       return Future<ProcessResult>.value(mockProcessResult);
     });
     initializeFakePackages();
     processRunner = RecordingProcessRunner();
-    plugins = [];
+    plugins = <String>[];
     final SamplePluginCommand samplePluginCommand = SamplePluginCommand(
       plugins,
       mockPackagesDir,
@@ -43,7 +44,7 @@ void main() {
       gitDir: gitDir,
     );
     runner =
-        CommandRunner<Null>('common_command', 'Test for common functionality');
+        CommandRunner<void>('common_command', 'Test for common functionality');
     runner.addCommand(samplePluginCommand);
   });
 
@@ -108,7 +109,7 @@ void main() {
 
     test('all plugins should be tested if there are no plugin related changes.',
         () async {
-      gitDiffResponse = ".cirrus";
+      gitDiffResponse = '.cirrus';
       final Directory plugin1 = createFakePlugin('plugin1');
       final Directory plugin2 = createFakePlugin('plugin2');
       await runner.run(
@@ -118,7 +119,7 @@ void main() {
     });
 
     test('Only changed plugin should be tested.', () async {
-      gitDiffResponse = "packages/plugin1/plugin1.dart";
+      gitDiffResponse = 'packages/plugin1/plugin1.dart';
       final Directory plugin1 = createFakePlugin('plugin1');
       createFakePlugin('plugin2');
       await runner.run(
@@ -226,12 +227,14 @@ packages/plugin3/plugin3.dart
       gitDiffResponse = '';
       gitDir = MockGitDir();
       when(gitDir.runCommand(any)).thenAnswer((Invocation invocation) {
-        gitDirCommands.add(invocation.positionalArguments[0]);
+        gitDirCommands.add(invocation.positionalArguments[0] as List<String>);
         final MockProcessResult mockProcessResult = MockProcessResult();
         if (invocation.positionalArguments[0][0] == 'diff') {
-          when<String>(mockProcessResult.stdout).thenReturn(gitDiffResponse);
+          when<String>(mockProcessResult.stdout as String)
+              .thenReturn(gitDiffResponse);
         } else if (invocation.positionalArguments[0][0] == 'merge-base') {
-          when<String>(mockProcessResult.stdout).thenReturn(mergeBaseResponse);
+          when<String>(mockProcessResult.stdout as String)
+              .thenReturn(mergeBaseResponse);
         }
         return Future<ProcessResult>.value(mockProcessResult);
       });
@@ -245,7 +248,7 @@ packages/plugin3/plugin3.dart
 
     test('No git diff should result no files changed', () async {
       final GitVersionFinder finder = GitVersionFinder(gitDir, 'some base sha');
-      List<String> changedFiles = await finder.getChangedFiles();
+      final List<String> changedFiles = await finder.getChangedFiles();
 
       expect(changedFiles, isEmpty);
     });
@@ -256,7 +259,7 @@ file1/file1.cc
 file2/file2.cc
 ''';
       final GitVersionFinder finder = GitVersionFinder(gitDir, 'some base sha');
-      List<String> changedFiles = await finder.getChangedFiles();
+      final List<String> changedFiles = await finder.getChangedFiles();
 
       expect(
           changedFiles, equals(<String>['file1/file1.cc', 'file2/file2.cc']));
@@ -268,7 +271,7 @@ file1/pubspec.yaml
 file2/file2.cc
 ''';
       final GitVersionFinder finder = GitVersionFinder(gitDir, 'some base sha');
-      List<String> changedFiles = await finder.getChangedPubSpecs();
+      final List<String> changedFiles = await finder.getChangedPubSpecs();
 
       expect(changedFiles, equals(<String>['file1/pubspec.yaml']));
     });
@@ -281,26 +284,27 @@ file2/file2.cc
 ''';
       final GitVersionFinder finder = GitVersionFinder(gitDir, null);
       await finder.getChangedFiles();
-      verify(gitDir
-          .runCommand(['diff', '--name-only', mergeBaseResponse, 'HEAD']));
+      verify(gitDir.runCommand(
+          <String>['diff', '--name-only', mergeBaseResponse, 'HEAD']));
     });
 
     test('use correct base sha if specified', () async {
-      final String customBaseSha = 'aklsjdcaskf12312';
+      const String customBaseSha = 'aklsjdcaskf12312';
       gitDiffResponse = '''
 file1/pubspec.yaml
 file2/file2.cc
 ''';
       final GitVersionFinder finder = GitVersionFinder(gitDir, customBaseSha);
       await finder.getChangedFiles();
-      verify(gitDir.runCommand(['diff', '--name-only', customBaseSha, 'HEAD']));
+      verify(gitDir
+          .runCommand(<String>['diff', '--name-only', customBaseSha, 'HEAD']));
     });
   });
 }
 
 class SamplePluginCommand extends PluginCommand {
   SamplePluginCommand(
-    this.plugins_,
+    this._plugins,
     Directory packagesDir,
     FileSystem fileSystem, {
     ProcessRunner processRunner = const ProcessRunner(),
@@ -308,7 +312,7 @@ class SamplePluginCommand extends PluginCommand {
   }) : super(packagesDir, fileSystem,
             processRunner: processRunner, gitDir: gitDir);
 
-  List<String> plugins_;
+  final List<String> _plugins;
 
   @override
   final String name = 'sample';
@@ -317,9 +321,9 @@ class SamplePluginCommand extends PluginCommand {
   final String description = 'sample command';
 
   @override
-  Future<Null> run() async {
-    await for (Directory package in getPlugins()) {
-      this.plugins_.add(package.path);
+  Future<void> run() async {
+    await for (final Directory package in getPlugins()) {
+      _plugins.add(package.path);
     }
   }
 }
diff --git a/script/tool/test/create_all_plugins_app_command_test.dart b/script/tool/test/create_all_plugins_app_command_test.dart
index 58f24c9a3de1..fedc04684631 100644
--- a/script/tool/test/create_all_plugins_app_command_test.dart
+++ b/script/tool/test/create_all_plugins_app_command_test.dart
@@ -12,7 +12,7 @@ import 'util.dart';
 
 void main() {
   group('$CreateAllPluginsAppCommand', () {
-    CommandRunner<Null> runner;
+    CommandRunner<void> runner;
     FileSystem fileSystem;
     Directory testRoot;
     Directory packagesDir;
@@ -22,7 +22,7 @@ void main() {
       // Since the core of this command is a call to 'flutter create', the test
       // has to use the real filesystem. Put everything possible in a unique
       // temporary to minimize affect on the host system.
-      fileSystem = LocalFileSystem();
+      fileSystem = const LocalFileSystem();
       testRoot = fileSystem.systemTempDirectory.createTempSync();
       packagesDir = testRoot.childDirectory('packages');
 
@@ -32,7 +32,7 @@ void main() {
         pluginsRoot: testRoot,
       );
       appDir = command.appDirectory;
-      runner = CommandRunner<Null>(
+      runner = CommandRunner<void>(
           'create_all_test', 'Test for $CreateAllPluginsAppCommand');
       runner.addCommand(command);
     });
diff --git a/script/tool/test/drive_examples_command_test.dart b/script/tool/test/drive_examples_command_test.dart
index 58b8fb0d087d..c5960b2c342e 100644
--- a/script/tool/test/drive_examples_command_test.dart
+++ b/script/tool/test/drive_examples_command_test.dart
@@ -14,10 +14,10 @@ import 'util.dart';
 
 void main() {
   group('test drive_example_command', () {
-    CommandRunner<Null> runner;
+    CommandRunner<void> runner;
     RecordingProcessRunner processRunner;
     final String flutterCommand =
-        LocalPlatform().isWindows ? 'flutter.bat' : 'flutter';
+        const LocalPlatform().isWindows ? 'flutter.bat' : 'flutter';
     setUp(() {
       initializeFakePackages();
       processRunner = RecordingProcessRunner();
@@ -25,7 +25,7 @@ void main() {
           mockPackagesDir, mockFileSystem,
           processRunner: processRunner);
 
-      runner = CommandRunner<Null>(
+      runner = CommandRunner<void>(
           'drive_examples_command', 'Test for drive_example_command');
       runner.addCommand(command);
     });
@@ -60,8 +60,8 @@ void main() {
         ]),
       );
 
-      String deviceTestPath = p.join('test', 'plugin.dart');
-      String driverTestPath = p.join('test_driver', 'plugin_test.dart');
+      final String deviceTestPath = p.join('test', 'plugin.dart');
+      final String driverTestPath = p.join('test_driver', 'plugin_test.dart');
       print(processRunner.recordedCalls);
       expect(
           processRunner.recordedCalls,
@@ -105,8 +105,8 @@ void main() {
         ]),
       );
 
-      String deviceTestPath = p.join('test_driver', 'plugin.dart');
-      String driverTestPath = p.join('test_driver', 'plugin_test.dart');
+      final String deviceTestPath = p.join('test_driver', 'plugin.dart');
+      final String driverTestPath = p.join('test_driver', 'plugin_test.dart');
       print(processRunner.recordedCalls);
       expect(
           processRunner.recordedCalls,
@@ -173,7 +173,8 @@ void main() {
         ]),
       );
 
-      String driverTestPath = p.join('test_driver', 'integration_test.dart');
+      final String driverTestPath =
+          p.join('test_driver', 'integration_test.dart');
       print(processRunner.recordedCalls);
       expect(
           processRunner.recordedCalls,
@@ -259,8 +260,8 @@ void main() {
         ]),
       );
 
-      String deviceTestPath = p.join('test_driver', 'plugin.dart');
-      String driverTestPath = p.join('test_driver', 'plugin_test.dart');
+      final String deviceTestPath = p.join('test_driver', 'plugin.dart');
+      final String driverTestPath = p.join('test_driver', 'plugin_test.dart');
       print(processRunner.recordedCalls);
       expect(
           processRunner.recordedCalls,
@@ -336,8 +337,8 @@ void main() {
         ]),
       );
 
-      String deviceTestPath = p.join('test_driver', 'plugin.dart');
-      String driverTestPath = p.join('test_driver', 'plugin_test.dart');
+      final String deviceTestPath = p.join('test_driver', 'plugin.dart');
+      final String driverTestPath = p.join('test_driver', 'plugin_test.dart');
       print(processRunner.recordedCalls);
       expect(
           processRunner.recordedCalls,
@@ -415,8 +416,8 @@ void main() {
         ]),
       );
 
-      String deviceTestPath = p.join('test_driver', 'plugin.dart');
-      String driverTestPath = p.join('test_driver', 'plugin_test.dart');
+      final String deviceTestPath = p.join('test_driver', 'plugin.dart');
+      final String driverTestPath = p.join('test_driver', 'plugin_test.dart');
       print(processRunner.recordedCalls);
       expect(
           processRunner.recordedCalls,
@@ -496,8 +497,8 @@ void main() {
         ]),
       );
 
-      String deviceTestPath = p.join('test_driver', 'plugin.dart');
-      String driverTestPath = p.join('test_driver', 'plugin_test.dart');
+      final String deviceTestPath = p.join('test_driver', 'plugin.dart');
+      final String driverTestPath = p.join('test_driver', 'plugin_test.dart');
       print(processRunner.recordedCalls);
       expect(
           processRunner.recordedCalls,
@@ -567,8 +568,8 @@ void main() {
         '--enable-experiment=exp1',
       ]);
 
-      String deviceTestPath = p.join('test', 'plugin.dart');
-      String driverTestPath = p.join('test_driver', 'plugin_test.dart');
+      final String deviceTestPath = p.join('test', 'plugin.dart');
+      final String driverTestPath = p.join('test_driver', 'plugin_test.dart');
       print(processRunner.recordedCalls);
       expect(
           processRunner.recordedCalls,
diff --git a/script/tool/test/firebase_test_lab_test.dart b/script/tool/test/firebase_test_lab_test.dart
index f1141ae19d80..d6068691d549 100644
--- a/script/tool/test/firebase_test_lab_test.dart
+++ b/script/tool/test/firebase_test_lab_test.dart
@@ -15,7 +15,7 @@ import 'util.dart';
 void main() {
   group('$FirebaseTestLabCommand', () {
     final List<String> printedMessages = <String>[];
-    CommandRunner<FirebaseTestLabCommand> runner;
+    CommandRunner<void> runner;
     RecordingProcessRunner processRunner;
 
     setUp(() {
@@ -26,7 +26,7 @@ void main() {
           processRunner: processRunner,
           print: (Object message) => printedMessages.add(message.toString()));
 
-      runner = CommandRunner<Null>(
+      runner = CommandRunner<void>(
           'firebase_test_lab_command', 'Test for $FirebaseTestLabCommand');
       runner.addCommand(command);
     });
@@ -60,7 +60,7 @@ void main() {
       expect(
           printedMessages,
           contains(
-              "\nWarning: gcloud config set returned a non-zero exit code. Continuing anyway."));
+              '\nWarning: gcloud config set returned a non-zero exit code. Continuing anyway.'));
     });
 
     test('runs e2e tests', () async {
@@ -86,7 +86,7 @@ void main() {
         ],
       ]);
 
-      final List<String> output = await runCapturingPrint(runner, <String>[
+      await runCapturingPrint(runner, <String>[
         'firebase-test-lab',
         '--device',
         'model=flame,version=29',
diff --git a/script/tool/test/java_test_command_test.dart b/script/tool/test/java_test_command_test.dart
index b036d7ec0c6f..ba016915223d 100644
--- a/script/tool/test/java_test_command_test.dart
+++ b/script/tool/test/java_test_command_test.dart
@@ -12,7 +12,7 @@ import 'util.dart';
 
 void main() {
   group('$JavaTestCommand', () {
-    CommandRunner<JavaTestCommand> runner;
+    CommandRunner<void> runner;
     final RecordingProcessRunner processRunner = RecordingProcessRunner();
 
     setUp(() {
@@ -22,7 +22,7 @@ void main() {
           processRunner: processRunner);
 
       runner =
-          CommandRunner<Null>('java_test_test', 'Test for $JavaTestCommand');
+          CommandRunner<void>('java_test_test', 'Test for $JavaTestCommand');
       runner.addCommand(command);
     });
 
@@ -50,7 +50,7 @@ void main() {
         orderedEquals(<ProcessCall>[
           ProcessCall(
             p.join(plugin.path, 'example/android/gradlew'),
-            <String>['testDebugUnitTest', '--info'],
+            const <String>['testDebugUnitTest', '--info'],
             p.join(plugin.path, 'example/android'),
           ),
         ]),
@@ -76,7 +76,7 @@ void main() {
         orderedEquals(<ProcessCall>[
           ProcessCall(
             p.join(plugin.path, 'example/android/gradlew'),
-            <String>['testDebugUnitTest', '--info'],
+            const <String>['testDebugUnitTest', '--info'],
             p.join(plugin.path, 'example/android'),
           ),
         ]),
diff --git a/script/tool/test/license_check_command_test.dart b/script/tool/test/license_check_command_test.dart
index f8646da5d83a..94606f54b764 100644
--- a/script/tool/test/license_check_command_test.dart
+++ b/script/tool/test/license_check_command_test.dart
@@ -11,7 +11,7 @@ import 'package:test/test.dart';
 
 void main() {
   group('$LicenseCheckCommand', () {
-    CommandRunner<Null> runner;
+    CommandRunner<void> runner;
     FileSystem fileSystem;
     List<String> printedMessages;
     Directory root;
@@ -29,7 +29,7 @@ void main() {
         print: (Object message) => printedMessages.add(message.toString()),
       );
       runner =
-          CommandRunner<Null>('license_test', 'Test for $LicenseCheckCommand');
+          CommandRunner<void>('license_test', 'Test for $LicenseCheckCommand');
       runner.addCommand(command);
     });
 
@@ -51,15 +51,15 @@ void main() {
         'found in the LICENSE file.',
       ],
     }) {
-      List<String> lines = ['$prefix$comment$copyright'];
-      for (String line in license) {
+      final List<String> lines = <String>['$prefix$comment$copyright'];
+      for (final String line in license) {
         lines.add('$comment$line');
       }
       file.writeAsStringSync(lines.join('\n') + suffix + '\n');
     }
 
     test('looks at only expected extensions', () async {
-      Map<String, bool> extensions = <String, bool>{
+      final Map<String, bool> extensions = <String, bool>{
         'c': true,
         'cc': true,
         'cpp': true,
@@ -98,7 +98,7 @@ void main() {
     });
 
     test('ignore list overrides extension matches', () async {
-      List<String> ignoredFiles = <String>[
+      final List<String> ignoredFiles = <String>[
         // Ignored base names.
         'flutter_export_environment.sh',
         'GeneratedPluginRegistrant.java',
@@ -124,11 +124,11 @@ void main() {
     });
 
     test('passes if all checked files have license blocks', () async {
-      File checked = root.childFile('checked.cc');
+      final File checked = root.childFile('checked.cc');
       checked.createSync();
       _writeLicense(checked);
-      File not_checked = root.childFile('not_checked.md');
-      not_checked.createSync();
+      final File notChecked = root.childFile('not_checked.md');
+      notChecked.createSync();
 
       await runner.run(<String>['license-check']);
 
@@ -138,15 +138,15 @@ void main() {
     });
 
     test('handles the comment styles for all supported languages', () async {
-      File file_a = root.childFile('file_a.cc');
-      file_a.createSync();
-      _writeLicense(file_a, comment: '// ');
-      File file_b = root.childFile('file_b.sh');
-      file_b.createSync();
-      _writeLicense(file_b, comment: '# ');
-      File file_c = root.childFile('file_c.html');
-      file_c.createSync();
-      _writeLicense(file_c, comment: '', prefix: '<!-- ', suffix: ' -->');
+      final File fileA = root.childFile('file_a.cc');
+      fileA.createSync();
+      _writeLicense(fileA, comment: '// ');
+      final File fileB = root.childFile('file_b.sh');
+      fileB.createSync();
+      _writeLicense(fileB, comment: '# ');
+      final File fileC = root.childFile('file_c.html');
+      fileC.createSync();
+      _writeLicense(fileC, comment: '', prefix: '<!-- ', suffix: ' -->');
 
       await runner.run(<String>['license-check']);
 
@@ -158,12 +158,12 @@ void main() {
     });
 
     test('fails if any checked files are missing license blocks', () async {
-      File good_a = root.childFile('good.cc');
-      good_a.createSync();
-      _writeLicense(good_a);
-      File good_b = root.childFile('good.h');
-      good_b.createSync();
-      _writeLicense(good_b);
+      final File goodA = root.childFile('good.cc');
+      goodA.createSync();
+      _writeLicense(goodA);
+      final File goodB = root.childFile('good.h');
+      goodB.createSync();
+      _writeLicense(goodB);
       root.childFile('bad.cc').createSync();
       root.childFile('bad.h').createSync();
 
@@ -183,10 +183,10 @@ void main() {
     });
 
     test('fails if any checked files are missing just the copyright', () async {
-      File good = root.childFile('good.cc');
+      final File good = root.childFile('good.cc');
       good.createSync();
       _writeLicense(good);
-      File bad = root.childFile('bad.cc');
+      final File bad = root.childFile('bad.cc');
       bad.createSync();
       _writeLicense(bad, copyright: '');
 
@@ -205,10 +205,10 @@ void main() {
     });
 
     test('fails if any checked files are missing just the license', () async {
-      File good = root.childFile('good.cc');
+      final File good = root.childFile('good.cc');
       good.createSync();
       _writeLicense(good);
-      File bad = root.childFile('bad.cc');
+      final File bad = root.childFile('bad.cc');
       bad.createSync();
       _writeLicense(bad, license: <String>[]);
 
@@ -228,7 +228,7 @@ void main() {
 
     test('fails if any third-party code is not in a third_party directory',
         () async {
-      File thirdPartyFile = root.childFile('third_party.cc');
+      final File thirdPartyFile = root.childFile('third_party.cc');
       thirdPartyFile.createSync();
       _writeLicense(thirdPartyFile, copyright: 'Copyright 2017 Someone Else');
 
@@ -247,7 +247,7 @@ void main() {
     });
 
     test('succeeds for third-party code in a third_party directory', () async {
-      File thirdPartyFile = root
+      final File thirdPartyFile = root
           .childDirectory('a_plugin')
           .childDirectory('lib')
           .childDirectory('src')
@@ -270,10 +270,10 @@ void main() {
     });
 
     test('fails for licenses that the tool does not expect', () async {
-      File good = root.childFile('good.cc');
+      final File good = root.childFile('good.cc');
       good.createSync();
       _writeLicense(good);
-      File bad = root.childDirectory('third_party').childFile('bad.cc');
+      final File bad = root.childDirectory('third_party').childFile('bad.cc');
       bad.createSync(recursive: true);
       _writeLicense(bad, license: <String>[
         'This program is free software: you can redistribute it and/or modify',
@@ -296,26 +296,28 @@ void main() {
 
     test('Apache is not recognized for new authors without validation changes',
         () async {
-      File good = root.childFile('good.cc');
+      final File good = root.childFile('good.cc');
       good.createSync();
       _writeLicense(good);
-      File bad = root.childDirectory('third_party').childFile('bad.cc');
+      final File bad = root.childDirectory('third_party').childFile('bad.cc');
       bad.createSync(recursive: true);
       _writeLicense(
         bad,
         copyright: 'Copyright 2017 Some New Authors.',
-          license: <String>[
-            'Licensed under the Apache License, Version 2.0 (the "License");',
-            'you may not use this file except in compliance with the License.'
-          ],
+        license: <String>[
+          'Licensed under the Apache License, Version 2.0 (the "License");',
+          'you may not use this file except in compliance with the License.'
+        ],
       );
 
       await expectLater(() => runner.run(<String>['license-check']),
           throwsA(const TypeMatcher<ToolExit>()));
 
       // Failure should give information about the problematic files.
-      expect(printedMessages,
-          contains('No recognized license was found for the following third-party files:'));
+      expect(
+          printedMessages,
+          contains(
+              'No recognized license was found for the following third-party files:'));
       expect(printedMessages, contains('  third_party/bad.cc'));
       // Failure shouldn't print the success message.
       expect(printedMessages,
@@ -324,7 +326,7 @@ void main() {
 
     test('passes if all first-party LICENSE files are correctly formatted',
         () async {
-      File license = root.childFile('LICENSE');
+      final File license = root.childFile('LICENSE');
       license.createSync();
       license.writeAsStringSync(_correctLicenseFileText);
 
@@ -337,7 +339,7 @@ void main() {
 
     test('fails if any first-party LICENSE files are incorrectly formatted',
         () async {
-      File license = root.childFile('LICENSE');
+      final File license = root.childFile('LICENSE');
       license.createSync();
       license.writeAsStringSync(_incorrectLicenseFileText);
 
@@ -349,7 +351,8 @@ void main() {
     });
 
     test('ignores third-party LICENSE format', () async {
-      File license = root.childDirectory('third_party').childFile('LICENSE');
+      final File license =
+          root.childDirectory('third_party').childFile('LICENSE');
       license.createSync(recursive: true);
       license.writeAsStringSync(_incorrectLicenseFileText);
 
@@ -362,8 +365,8 @@ void main() {
   });
 }
 
-const String _correctLicenseFileText =
-    '''Copyright 2013 The Flutter Authors. All rights reserved.
+const String _correctLicenseFileText = '''
+Copyright 2013 The Flutter Authors. All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modification,
 are permitted provided that the following conditions are met:
@@ -392,8 +395,8 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // A common incorrect version created by copying text intended for a code file,
 // with comment markers.
-const String _incorrectLicenseFileText =
-    '''// Copyright 2013 The Flutter Authors. All rights reserved.
+const String _incorrectLicenseFileText = '''
+// Copyright 2013 The Flutter Authors. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
diff --git a/script/tool/test/lint_podspecs_command_test.dart b/script/tool/test/lint_podspecs_command_test.dart
index 5475641cba93..a1fa1f7c7743 100644
--- a/script/tool/test/lint_podspecs_command_test.dart
+++ b/script/tool/test/lint_podspecs_command_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:io';
-
 import 'package:args/command_runner.dart';
 import 'package:file/file.dart';
 import 'package:flutter_plugin_tools/src/lint_podspecs_command.dart';
@@ -17,7 +15,7 @@ import 'util.dart';
 
 void main() {
   group('$LintPodspecsCommand', () {
-    CommandRunner<Null> runner;
+    CommandRunner<void> runner;
     MockPlatform mockPlatform;
     final RecordingProcessRunner processRunner = RecordingProcessRunner();
     List<String> printedMessages;
@@ -37,7 +35,7 @@ void main() {
       );
 
       runner =
-          CommandRunner<Null>('podspec_test', 'Test for $LintPodspecsCommand');
+          CommandRunner<void>('podspec_test', 'Test for $LintPodspecsCommand');
       runner.addCommand(command);
       final MockProcess mockLintProcess = MockProcess();
       mockLintProcess.exitCodeCompleter.complete(0);
@@ -64,7 +62,7 @@ void main() {
     });
 
     test('runs pod lib lint on a podspec', () async {
-      Directory plugin1Dir =
+      final Directory plugin1Dir =
           createFakePlugin('plugin1', withExtraFiles: <List<String>>[
         <String>['ios', 'plugin1.podspec'],
         <String>['bogus.dart'], // Ignore non-podspecs.
@@ -78,7 +76,7 @@ void main() {
       expect(
         processRunner.recordedCalls,
         orderedEquals(<ProcessCall>[
-          ProcessCall('which', <String>['pod'], mockPackagesDir.path),
+          ProcessCall('which', const <String>['pod'], mockPackagesDir.path),
           ProcessCall(
               'pod',
               <String>[
@@ -103,8 +101,7 @@ void main() {
         ]),
       );
 
-      expect(
-          printedMessages, contains('Linting plugin1.podspec'));
+      expect(printedMessages, contains('Linting plugin1.podspec'));
       expect(printedMessages, contains('Foo'));
       expect(printedMessages, contains('Bar'));
     });
@@ -123,13 +120,13 @@ void main() {
       expect(
         processRunner.recordedCalls,
         orderedEquals(<ProcessCall>[
-          ProcessCall('which', <String>['pod'], mockPackagesDir.path),
+          ProcessCall('which', const <String>['pod'], mockPackagesDir.path),
         ]),
       );
     });
 
     test('allow warnings for podspecs with known warnings', () async {
-      Directory plugin1Dir =
+      final Directory plugin1Dir =
           createFakePlugin('plugin1', withExtraFiles: <List<String>>[
         <String>['plugin1.podspec'],
       ]);
@@ -139,7 +136,7 @@ void main() {
       expect(
         processRunner.recordedCalls,
         orderedEquals(<ProcessCall>[
-          ProcessCall('which', <String>['pod'], mockPackagesDir.path),
+          ProcessCall('which', const <String>['pod'], mockPackagesDir.path),
           ProcessCall(
               'pod',
               <String>[
@@ -166,8 +163,7 @@ void main() {
         ]),
       );
 
-      expect(
-          printedMessages, contains('Linting plugin1.podspec'));
+      expect(printedMessages, contains('Linting plugin1.podspec'));
     });
   });
 }
diff --git a/script/tool/test/list_command_test.dart b/script/tool/test/list_command_test.dart
index 19e9df0dd38d..e7fcfe7a7c4b 100644
--- a/script/tool/test/list_command_test.dart
+++ b/script/tool/test/list_command_test.dart
@@ -11,13 +11,13 @@ import 'util.dart';
 
 void main() {
   group('$ListCommand', () {
-    CommandRunner<ListCommand> runner;
+    CommandRunner<void> runner;
 
     setUp(() {
       initializeFakePackages();
       final ListCommand command = ListCommand(mockPackagesDir, mockFileSystem);
 
-      runner = CommandRunner<Null>('list_test', 'Test for $ListCommand');
+      runner = CommandRunner<void>('list_test', 'Test for $ListCommand');
       runner.addCommand(command);
     });
 
diff --git a/script/tool/test/mocks.dart b/script/tool/test/mocks.dart
index 2ef9d72e3637..ad1f357fb472 100644
--- a/script/tool/test/mocks.dart
+++ b/script/tool/test/mocks.dart
@@ -33,5 +33,5 @@ class MockIOSink extends Mock implements IOSink {
   List<String> lines = <String>[];
 
   @override
-  void writeln([Object obj = ""]) => lines.add(obj);
+  void writeln([Object obj = '']) => lines.add(obj.toString());
 }
diff --git a/script/tool/test/publish_check_command_test.dart b/script/tool/test/publish_check_command_test.dart
index dbe6e2cfe548..568d35eeff29 100644
--- a/script/tool/test/publish_check_command_test.dart
+++ b/script/tool/test/publish_check_command_test.dart
@@ -17,7 +17,7 @@ import 'util.dart';
 void main() {
   group('$PublishCheckProcessRunner tests', () {
     PublishCheckProcessRunner processRunner;
-    CommandRunner runner;
+    CommandRunner<void> runner;
 
     setUp(() {
       initializeFakePackages();
@@ -26,7 +26,7 @@ void main() {
           mockPackagesDir, mockFileSystem,
           processRunner: processRunner);
 
-      runner = CommandRunner<Null>(
+      runner = CommandRunner<void>(
         'publish_check_command',
         'Test for publish-check command.',
       );
@@ -38,8 +38,8 @@ void main() {
     });
 
     test('publish check all packages', () async {
-      final Directory plugin1Dir = await createFakePlugin('a');
-      final Directory plugin2Dir = await createFakePlugin('b');
+      final Directory plugin1Dir = createFakePlugin('a');
+      final Directory plugin2Dir = createFakePlugin('b');
 
       processRunner.processesToReturn.add(
         MockProcess()..exitCodeCompleter.complete(0),
@@ -52,15 +52,19 @@ void main() {
       expect(
           processRunner.recordedCalls,
           orderedEquals(<ProcessCall>[
-            ProcessCall('flutter',
-                <String>['pub', 'publish', '--', '--dry-run'], plugin1Dir.path),
-            ProcessCall('flutter',
-                <String>['pub', 'publish', '--', '--dry-run'], plugin2Dir.path),
+            ProcessCall(
+                'flutter',
+                const <String>['pub', 'publish', '--', '--dry-run'],
+                plugin1Dir.path),
+            ProcessCall(
+                'flutter',
+                const <String>['pub', 'publish', '--', '--dry-run'],
+                plugin2Dir.path),
           ]));
     });
 
     test('fail on negative test', () async {
-      await createFakePlugin('a');
+      createFakePlugin('a');
 
       final MockProcess process = MockProcess();
       process.stdoutController.close(); // ignore: unawaited_futures
@@ -76,7 +80,7 @@ void main() {
     });
 
     test('fail on bad pubspec', () async {
-      final Directory dir = await createFakePlugin('c');
+      final Directory dir = createFakePlugin('c');
       await dir.childFile('pubspec.yaml').writeAsString('bad-yaml');
 
       final MockProcess process = MockProcess();
@@ -87,9 +91,9 @@ void main() {
     });
 
     test('pass on prerelease', () async {
-      await createFakePlugin('d');
+      createFakePlugin('d');
 
-      final String preReleaseOutput = 'Package has 1 warning.'
+      const String preReleaseOutput = 'Package has 1 warning.'
           'Packages with an SDK constraint on a pre-release of the Dart SDK should themselves be published as a pre-release version.';
 
       final MockProcess process = MockProcess();
diff --git a/script/tool/test/publish_plugin_command_test.dart b/script/tool/test/publish_plugin_command_test.dart
index cfa40b9dc0a5..03e7858d3bcd 100644
--- a/script/tool/test/publish_plugin_command_test.dart
+++ b/script/tool/test/publish_plugin_command_test.dart
@@ -27,7 +27,7 @@ void main() {
   Directory pluginDir;
   GitDir gitDir;
   TestProcessRunner processRunner;
-  CommandRunner<Null> commandRunner;
+  CommandRunner<void> commandRunner;
   MockStdin mockStdin;
 
   setUp(() async {
@@ -48,7 +48,7 @@ void main() {
     await gitDir.runCommand(<String>['commit', '-m', 'Initial commit']);
     processRunner = TestProcessRunner();
     mockStdin = MockStdin();
-    commandRunner = CommandRunner<Null>('tester', '')
+    commandRunner = CommandRunner<void>('tester', '')
       ..addCommand(PublishPluginCommand(
           mockPackagesDir, mockPackagesDir.fileSystem,
           processRunner: processRunner,
@@ -66,13 +66,17 @@ void main() {
       await expectLater(() => commandRunner.run(<String>['publish-plugin']),
           throwsA(const TypeMatcher<ToolExit>()));
       expect(
-          printedMessages.last, contains("Must specify a package to publish."));
+          printedMessages.last, contains('Must specify a package to publish.'));
     });
 
     test('requires an existing flag', () async {
       await expectLater(
-          () => commandRunner
-              .run(<String>['publish-plugin', '--package', 'iamerror', '--no-push-tags']),
+          () => commandRunner.run(<String>[
+                'publish-plugin',
+                '--package',
+                'iamerror',
+                '--no-push-tags'
+              ]),
           throwsA(const TypeMatcher<ToolExit>()));
 
       expect(printedMessages.last, contains('iamerror does not exist'));
@@ -82,8 +86,12 @@ void main() {
       pluginDir.childFile('tmp').createSync();
 
       await expectLater(
-          () => commandRunner
-              .run(<String>['publish-plugin', '--package', testPluginName, '--no-push-tags']),
+          () => commandRunner.run(<String>[
+                'publish-plugin',
+                '--package',
+                testPluginName,
+                '--no-push-tags'
+              ]),
           throwsA(const TypeMatcher<ToolExit>()));
 
       expect(
@@ -97,7 +105,7 @@ void main() {
           () => commandRunner
               .run(<String>['publish-plugin', '--package', testPluginName]),
           throwsA(const TypeMatcher<ToolExit>()));
-      expect(processRunner.results.last.stderr, contains("No such remote"));
+      expect(processRunner.results.last.stderr, contains('No such remote'));
     });
 
     test("doesn't validate the remote if it's not pushing tags", () async {
@@ -202,7 +210,7 @@ void main() {
               ]),
           throwsA(const TypeMatcher<ToolExit>()));
 
-      expect(printedMessages, contains("Publish failed. Exiting."));
+      expect(printedMessages, contains('Publish failed. Exiting.'));
     });
   });
 
@@ -218,7 +226,7 @@ void main() {
 
       final String tag =
           (await gitDir.runCommand(<String>['show-ref', 'fake_package-v0.0.1']))
-              .stdout;
+              .stdout as String;
       expect(tag, isNotEmpty);
     });
 
@@ -233,11 +241,11 @@ void main() {
               ]),
           throwsA(const TypeMatcher<ToolExit>()));
 
-      expect(printedMessages, contains("Publish failed. Exiting."));
+      expect(printedMessages, contains('Publish failed. Exiting.'));
       final String tag = (await gitDir.runCommand(
               <String>['show-ref', 'fake_package-v0.0.1'],
               throwOnError: false))
-          .stdout;
+          .stdout as String;
       expect(tag, isEmpty);
     });
   });
@@ -359,7 +367,7 @@ class MockStdin extends Mock implements io.Stdin {
   String readLineOutput;
 
   @override
-  Stream<S> transform<S>(StreamTransformer<dynamic, S> streamTransformer) {
+  Stream<S> transform<S>(StreamTransformer<List<int>, S> streamTransformer) {
     return controller.stream.transform(streamTransformer);
   }
 
diff --git a/script/tool/test/test_command_test.dart b/script/tool/test/test_command_test.dart
index 66471263f661..1dd0c158293a 100644
--- a/script/tool/test/test_command_test.dart
+++ b/script/tool/test/test_command_test.dart
@@ -11,7 +11,7 @@ import 'util.dart';
 
 void main() {
   group('$TestCommand', () {
-    CommandRunner<TestCommand> runner;
+    CommandRunner<void> runner;
     final RecordingProcessRunner processRunner = RecordingProcessRunner();
 
     setUp(() {
@@ -19,7 +19,7 @@ void main() {
       final TestCommand command = TestCommand(mockPackagesDir, mockFileSystem,
           processRunner: processRunner);
 
-      runner = CommandRunner<Null>('test_test', 'Test for $TestCommand');
+      runner = CommandRunner<void>('test_test', 'Test for $TestCommand');
       runner.addCommand(command);
     });
 
@@ -43,8 +43,10 @@ void main() {
       expect(
         processRunner.recordedCalls,
         orderedEquals(<ProcessCall>[
-          ProcessCall('flutter', <String>['test', '--color'], plugin1Dir.path),
-          ProcessCall('flutter', <String>['test', '--color'], plugin2Dir.path),
+          ProcessCall(
+              'flutter', const <String>['test', '--color'], plugin1Dir.path),
+          ProcessCall(
+              'flutter', const <String>['test', '--color'], plugin2Dir.path),
         ]),
       );
 
@@ -63,7 +65,8 @@ void main() {
       expect(
         processRunner.recordedCalls,
         orderedEquals(<ProcessCall>[
-          ProcessCall('flutter', <String>['test', '--color'], plugin2Dir.path),
+          ProcessCall(
+              'flutter', const <String>['test', '--color'], plugin2Dir.path),
         ]),
       );
 
@@ -89,12 +92,12 @@ void main() {
         orderedEquals(<ProcessCall>[
           ProcessCall(
               'flutter',
-              <String>['test', '--color', '--enable-experiment=exp1'],
+              const <String>['test', '--color', '--enable-experiment=exp1'],
               plugin1Dir.path),
-          ProcessCall('pub', <String>['get'], plugin2Dir.path),
+          ProcessCall('pub', const <String>['get'], plugin2Dir.path),
           ProcessCall(
               'pub',
-              <String>['run', '--enable-experiment=exp1', 'test'],
+              const <String>['run', '--enable-experiment=exp1', 'test'],
               plugin2Dir.path),
         ]),
       );
@@ -117,8 +120,10 @@ void main() {
       expect(
         processRunner.recordedCalls,
         orderedEquals(<ProcessCall>[
-          ProcessCall('flutter',
-              <String>['test', '--color', '--platform=chrome'], pluginDir.path),
+          ProcessCall(
+              'flutter',
+              const <String>['test', '--color', '--platform=chrome'],
+              pluginDir.path),
         ]),
       );
     });
@@ -142,12 +147,12 @@ void main() {
         orderedEquals(<ProcessCall>[
           ProcessCall(
               'flutter',
-              <String>['test', '--color', '--enable-experiment=exp1'],
+              const <String>['test', '--color', '--enable-experiment=exp1'],
               plugin1Dir.path),
-          ProcessCall('pub', <String>['get'], plugin2Dir.path),
+          ProcessCall('pub', const <String>['get'], plugin2Dir.path),
           ProcessCall(
               'pub',
-              <String>['run', '--enable-experiment=exp1', 'test'],
+              const <String>['run', '--enable-experiment=exp1', 'test'],
               plugin2Dir.path),
         ]),
       );
diff --git a/script/tool/test/util.dart b/script/tool/test/util.dart
index d02b756ee9c6..5a2c42bd3194 100644
--- a/script/tool/test/util.dart
+++ b/script/tool/test/util.dart
@@ -3,11 +3,13 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io' as io;
 
 import 'package:args/command_runner.dart';
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
+import 'package:meta/meta.dart';
 import 'package:platform/platform.dart';
 import 'package:flutter_plugin_tools/src/common.dart';
 import 'package:quiver/collection.dart';
@@ -16,7 +18,7 @@ import 'package:quiver/collection.dart';
 // for each test, to eliminate the chance of files from one test interfering
 // with another test.
 FileSystem mockFileSystem = MemoryFileSystem(
-    style: LocalPlatform().isWindows
+    style: const LocalPlatform().isWindows
         ? FileSystemStyle.windows
         : FileSystemStyle.posix);
 Directory mockPackagesDir;
@@ -83,20 +85,19 @@ Directory createFakePlugin(
     final Directory exampleDir = pluginDirectory.childDirectory('example')
       ..createSync();
     createFakePubspec(exampleDir,
-        name: "${name}_example", isFlutter: isFlutter);
+        name: '${name}_example', isFlutter: isFlutter);
   } else if (withExamples.isNotEmpty) {
     final Directory exampleDir = pluginDirectory.childDirectory('example')
       ..createSync();
-    for (String example in withExamples) {
+    for (final String example in withExamples) {
       final Directory currentExample = exampleDir.childDirectory(example)
         ..createSync();
       createFakePubspec(currentExample, name: example, isFlutter: isFlutter);
     }
   }
 
-  for (List<String> file in withExtraFiles) {
-    final List<String> newFilePath = <String>[pluginDirectory.path]
-      ..addAll(file);
+  for (final List<String> file in withExtraFiles) {
+    final List<String> newFilePath = <String>[pluginDirectory.path, ...file];
     final File newFile =
         mockFileSystem.file(mockFileSystem.path.joinAll(newFilePath));
     newFile.createSync(recursive: true);
@@ -195,7 +196,7 @@ void cleanupPackages() {
 /// Run the command [runner] with the given [args] and return
 /// what was printed.
 Future<List<String>> runCapturingPrint(
-    CommandRunner<PluginCommand> runner, List<String> args) async {
+    CommandRunner<void> runner, List<String> args) async {
   final List<String> prints = <String>[];
   final ZoneSpecification spec = ZoneSpecification(
     print: (_, __, ___, String message) {
@@ -237,8 +238,8 @@ class RecordingProcessRunner extends ProcessRunner {
   Future<io.ProcessResult> run(String executable, List<String> args,
       {Directory workingDir,
       bool exitOnError = false,
-      stdoutEncoding = io.systemEncoding,
-      stderrEncoding = io.systemEncoding}) async {
+      Encoding stdoutEncoding = io.systemEncoding,
+      Encoding stderrEncoding = io.systemEncoding}) async {
     recordedCalls.add(ProcessCall(executable, args, workingDir?.path));
     io.ProcessResult result;
 
@@ -279,6 +280,7 @@ class RecordingProcessRunner extends ProcessRunner {
 }
 
 /// A recorded process call.
+@immutable
 class ProcessCall {
   const ProcessCall(this.executable, this.args, this.workingDir);
 
@@ -293,13 +295,10 @@ class ProcessCall {
 
   @override
   bool operator ==(dynamic other) {
-    if (other is! ProcessCall) {
-      return false;
-    }
-    final ProcessCall otherCall = other;
-    return executable == otherCall.executable &&
-        listsEqual(args, otherCall.args) &&
-        workingDir == otherCall.workingDir;
+    return other is ProcessCall &&
+        executable == other.executable &&
+        listsEqual(args, other.args) &&
+        workingDir == other.workingDir;
   }
 
   @override
@@ -311,7 +310,7 @@ class ProcessCall {
 
   @override
   String toString() {
-    final List<String> command = <String>[executable]..addAll(args);
+    final List<String> command = <String>[executable, ...args];
     return '"${command.join(' ')}" in $workingDir';
   }
 }
diff --git a/script/tool/test/version_check_test.dart b/script/tool/test/version_check_test.dart
index dc36c6c32284..96a460d7e729 100644
--- a/script/tool/test/version_check_test.dart
+++ b/script/tool/test/version_check_test.dart
@@ -3,14 +3,15 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:io';
+import 'dart:io' as io;
 
 import 'package:args/command_runner.dart';
+import 'package:file/file.dart';
 import 'package:flutter_plugin_tools/src/common.dart';
 import 'package:git/git.dart';
 import 'package:mockito/mockito.dart';
-import "package:test/test.dart";
-import "package:flutter_plugin_tools/src/version_check_command.dart";
+import 'package:test/test.dart';
+import 'package:flutter_plugin_tools/src/version_check_command.dart';
 import 'package:pub_semver/pub_semver.dart';
 import 'util.dart';
 
@@ -36,11 +37,11 @@ void testAllowedVersion(
 
 class MockGitDir extends Mock implements GitDir {}
 
-class MockProcessResult extends Mock implements ProcessResult {}
+class MockProcessResult extends Mock implements io.ProcessResult {}
 
 void main() {
   group('$VersionCheckCommand', () {
-    CommandRunner<VersionCheckCommand> runner;
+    CommandRunner<void> runner;
     RecordingProcessRunner processRunner;
     List<List<String>> gitDirCommands;
     String gitDiffResponse;
@@ -52,16 +53,17 @@ void main() {
       gitShowResponses = <String, String>{};
       final MockGitDir gitDir = MockGitDir();
       when(gitDir.runCommand(any)).thenAnswer((Invocation invocation) {
-        gitDirCommands.add(invocation.positionalArguments[0]);
+        gitDirCommands.add(invocation.positionalArguments[0] as List<String>);
         final MockProcessResult mockProcessResult = MockProcessResult();
         if (invocation.positionalArguments[0][0] == 'diff') {
-          when<String>(mockProcessResult.stdout).thenReturn(gitDiffResponse);
+          when<String>(mockProcessResult.stdout as String)
+              .thenReturn(gitDiffResponse);
         } else if (invocation.positionalArguments[0][0] == 'show') {
           final String response =
               gitShowResponses[invocation.positionalArguments[0][1]];
-          when<String>(mockProcessResult.stdout).thenReturn(response);
+          when<String>(mockProcessResult.stdout as String).thenReturn(response);
         }
-        return Future<ProcessResult>.value(mockProcessResult);
+        return Future<io.ProcessResult>.value(mockProcessResult);
       });
       initializeFakePackages();
       processRunner = RecordingProcessRunner();
@@ -69,7 +71,7 @@ void main() {
           mockPackagesDir, mockFileSystem,
           processRunner: processRunner, gitDir: gitDir);
 
-      runner = CommandRunner<Null>(
+      runner = CommandRunner<void>(
           'version_check_command', 'Test for $VersionCheckCommand');
       runner.addCommand(command);
     });
@@ -80,7 +82,7 @@ void main() {
 
     test('allows valid version', () async {
       createFakePlugin('plugin', includeChangeLog: true, includeVersion: true);
-      gitDiffResponse = "packages/plugin/pubspec.yaml";
+      gitDiffResponse = 'packages/plugin/pubspec.yaml';
       gitShowResponses = <String, String>{
         'master:packages/plugin/pubspec.yaml': 'version: 1.0.0',
         'HEAD:packages/plugin/pubspec.yaml': 'version: 2.0.0',
@@ -105,7 +107,7 @@ void main() {
 
     test('denies invalid version', () async {
       createFakePlugin('plugin', includeChangeLog: true, includeVersion: true);
-      gitDiffResponse = "packages/plugin/pubspec.yaml";
+      gitDiffResponse = 'packages/plugin/pubspec.yaml';
       gitShowResponses = <String, String>{
         'master:packages/plugin/pubspec.yaml': 'version: 0.0.1',
         'HEAD:packages/plugin/pubspec.yaml': 'version: 0.2.0',
@@ -128,7 +130,7 @@ void main() {
 
     test('gracefully handles missing pubspec.yaml', () async {
       createFakePlugin('plugin', includeChangeLog: true, includeVersion: true);
-      gitDiffResponse = "packages/plugin/pubspec.yaml";
+      gitDiffResponse = 'packages/plugin/pubspec.yaml';
       mockFileSystem.currentDirectory
           .childDirectory('packages')
           .childDirectory('plugin')
@@ -152,7 +154,7 @@ void main() {
     test('allows minor changes to platform interfaces', () async {
       createFakePlugin('plugin_platform_interface',
           includeChangeLog: true, includeVersion: true);
-      gitDiffResponse = "packages/plugin_platform_interface/pubspec.yaml";
+      gitDiffResponse = 'packages/plugin_platform_interface/pubspec.yaml';
       gitShowResponses = <String, String>{
         'master:packages/plugin_platform_interface/pubspec.yaml':
             'version: 1.0.0',
@@ -181,7 +183,7 @@ void main() {
     test('disallows breaking changes to platform interfaces', () async {
       createFakePlugin('plugin_platform_interface',
           includeChangeLog: true, includeVersion: true);
-      gitDiffResponse = "packages/plugin_platform_interface/pubspec.yaml";
+      gitDiffResponse = 'packages/plugin_platform_interface/pubspec.yaml';
       gitShowResponses = <String, String>{
         'master:packages/plugin_platform_interface/pubspec.yaml':
             'version: 1.0.0',
@@ -214,7 +216,7 @@ void main() {
 
       createFakePubspec(pluginDirectory,
           isFlutter: true, includeVersion: true, version: '1.0.1');
-      String changelog = '''
+      const String changelog = '''
 
 
 
@@ -225,9 +227,9 @@ void main() {
       createFakeCHANGELOG(pluginDirectory, changelog);
       final List<String> output = await runCapturingPrint(
           runner, <String>['version-check', '--base-sha=master']);
-      await expect(
+      expect(
         output,
-        containsAllInOrder([
+        containsAllInOrder(<String>[
           'Checking the first version listed in CHANGELOG.MD matches the version in pubspec.yaml for plugin.',
           'plugin passed version check',
           'No version check errors found!'
@@ -243,7 +245,7 @@ void main() {
 
       createFakePubspec(pluginDirectory,
           isFlutter: true, includeVersion: true, version: '1.0.1');
-      String changelog = '''
+      const String changelog = '''
 ## 1.0.2
 
 * Some changes.
@@ -256,10 +258,10 @@ void main() {
         throwsA(const TypeMatcher<Error>()),
       );
       try {
-        List<String> outputValue = await output;
+        final List<String> outputValue = await output;
         await expectLater(
           outputValue,
-          containsAllInOrder([
+          containsAllInOrder(<String>[
             '''
   versions for plugin in CHANGELOG.md and pubspec.yaml do not match.
   The version in pubspec.yaml is 1.0.1.
@@ -278,7 +280,7 @@ void main() {
 
       createFakePubspec(pluginDirectory,
           isFlutter: true, includeVersion: true, version: '1.0.1');
-      String changelog = '''
+      const String changelog = '''
 ## 1.0.1
 
 * Some changes.
@@ -286,9 +288,9 @@ void main() {
       createFakeCHANGELOG(pluginDirectory, changelog);
       final List<String> output = await runCapturingPrint(
           runner, <String>['version-check', '--base-sha=master']);
-      await expect(
+      expect(
         output,
-        containsAllInOrder([
+        containsAllInOrder(<String>[
           'Checking the first version listed in CHANGELOG.MD matches the version in pubspec.yaml for plugin.',
           'plugin passed version check',
           'No version check errors found!'
@@ -306,7 +308,7 @@ void main() {
 
       createFakePubspec(pluginDirectory,
           isFlutter: true, includeVersion: true, version: '1.0.0');
-      String changelog = '''
+      const String changelog = '''
 ## 1.0.1
 
 * Some changes.
@@ -316,17 +318,17 @@ void main() {
 * Some other changes.
 ''';
       createFakeCHANGELOG(pluginDirectory, changelog);
-      Future<List<String>> output = runCapturingPrint(
+      final Future<List<String>> output = runCapturingPrint(
           runner, <String>['version-check', '--base-sha=master']);
       await expectLater(
         output,
         throwsA(const TypeMatcher<Error>()),
       );
       try {
-        List<String> outputValue = await output;
+        final List<String> outputValue = await output;
         await expectLater(
           outputValue,
-          containsAllInOrder([
+          containsAllInOrder(<String>[
             '''
   versions for plugin in CHANGELOG.md and pubspec.yaml do not match.
   The version in pubspec.yaml is 1.0.0.
@@ -338,122 +340,97 @@ void main() {
     });
   });
 
-  group("Pre 1.0", () {
-    test("nextVersion allows patch version", () {
-      testAllowedVersion("0.12.0", "0.12.0+1",
+  group('Pre 1.0', () {
+    test('nextVersion allows patch version', () {
+      testAllowedVersion('0.12.0', '0.12.0+1',
           nextVersionType: NextVersionType.PATCH);
-      testAllowedVersion("0.12.0+4", "0.12.0+5",
+      testAllowedVersion('0.12.0+4', '0.12.0+5',
           nextVersionType: NextVersionType.PATCH);
     });
 
-    test("nextVersion does not allow jumping patch", () {
-      testAllowedVersion("0.12.0", "0.12.0+2", allowed: false);
-      testAllowedVersion("0.12.0+2", "0.12.0+4", allowed: false);
+    test('nextVersion does not allow jumping patch', () {
+      testAllowedVersion('0.12.0', '0.12.0+2', allowed: false);
+      testAllowedVersion('0.12.0+2', '0.12.0+4', allowed: false);
     });
 
-    test("nextVersion does not allow going back", () {
-      testAllowedVersion("0.12.0", "0.11.0", allowed: false);
-      testAllowedVersion("0.12.0+2", "0.12.0+1", allowed: false);
-      testAllowedVersion("0.12.0+1", "0.12.0", allowed: false);
+    test('nextVersion does not allow going back', () {
+      testAllowedVersion('0.12.0', '0.11.0', allowed: false);
+      testAllowedVersion('0.12.0+2', '0.12.0+1', allowed: false);
+      testAllowedVersion('0.12.0+1', '0.12.0', allowed: false);
     });
 
-    test("nextVersion allows minor version", () {
-      testAllowedVersion("0.12.0", "0.12.1",
+    test('nextVersion allows minor version', () {
+      testAllowedVersion('0.12.0', '0.12.1',
           nextVersionType: NextVersionType.MINOR);
-      testAllowedVersion("0.12.0+4", "0.12.1",
+      testAllowedVersion('0.12.0+4', '0.12.1',
           nextVersionType: NextVersionType.MINOR);
     });
 
-    test("nextVersion does not allow jumping minor", () {
-      testAllowedVersion("0.12.0", "0.12.2", allowed: false);
-      testAllowedVersion("0.12.0+2", "0.12.3", allowed: false);
+    test('nextVersion does not allow jumping minor', () {
+      testAllowedVersion('0.12.0', '0.12.2', allowed: false);
+      testAllowedVersion('0.12.0+2', '0.12.3', allowed: false);
     });
   });
 
-  group("Releasing 1.0", () {
-    test("nextVersion allows releasing 1.0", () {
-      testAllowedVersion("0.12.0", "1.0.0",
+  group('Releasing 1.0', () {
+    test('nextVersion allows releasing 1.0', () {
+      testAllowedVersion('0.12.0', '1.0.0',
           nextVersionType: NextVersionType.BREAKING_MAJOR);
-      testAllowedVersion("0.12.0+4", "1.0.0",
+      testAllowedVersion('0.12.0+4', '1.0.0',
           nextVersionType: NextVersionType.BREAKING_MAJOR);
     });
 
-    test("nextVersion does not allow jumping major", () {
-      testAllowedVersion("0.12.0", "2.0.0", allowed: false);
-      testAllowedVersion("0.12.0+4", "2.0.0", allowed: false);
+    test('nextVersion does not allow jumping major', () {
+      testAllowedVersion('0.12.0', '2.0.0', allowed: false);
+      testAllowedVersion('0.12.0+4', '2.0.0', allowed: false);
     });
 
-    test("nextVersion does not allow un-releasing", () {
-      testAllowedVersion("1.0.0", "0.12.0+4", allowed: false);
-      testAllowedVersion("1.0.0", "0.12.0", allowed: false);
+    test('nextVersion does not allow un-releasing', () {
+      testAllowedVersion('1.0.0', '0.12.0+4', allowed: false);
+      testAllowedVersion('1.0.0', '0.12.0', allowed: false);
     });
   });
 
-  group("Post 1.0", () {
-    test("nextVersion allows patch jumps", () {
-      testAllowedVersion("1.0.1", "1.0.2",
+  group('Post 1.0', () {
+    test('nextVersion allows patch jumps', () {
+      testAllowedVersion('1.0.1', '1.0.2',
           nextVersionType: NextVersionType.PATCH);
-      testAllowedVersion("1.0.0", "1.0.1",
+      testAllowedVersion('1.0.0', '1.0.1',
           nextVersionType: NextVersionType.PATCH);
     });
 
-    test("nextVersion does not allow build jumps", () {
-      testAllowedVersion("1.0.1", "1.0.1+1", allowed: false);
-      testAllowedVersion("1.0.0+5", "1.0.0+6", allowed: false);
+    test('nextVersion does not allow build jumps', () {
+      testAllowedVersion('1.0.1', '1.0.1+1', allowed: false);
+      testAllowedVersion('1.0.0+5', '1.0.0+6', allowed: false);
     });
 
-    test("nextVersion does not allow skipping patches", () {
-      testAllowedVersion("1.0.1", "1.0.3", allowed: false);
-      testAllowedVersion("1.0.0", "1.0.6", allowed: false);
+    test('nextVersion does not allow skipping patches', () {
+      testAllowedVersion('1.0.1', '1.0.3', allowed: false);
+      testAllowedVersion('1.0.0', '1.0.6', allowed: false);
     });
 
-    test("nextVersion allows minor version jumps", () {
-      testAllowedVersion("1.0.1", "1.1.0",
+    test('nextVersion allows minor version jumps', () {
+      testAllowedVersion('1.0.1', '1.1.0',
           nextVersionType: NextVersionType.MINOR);
-      testAllowedVersion("1.0.0", "1.1.0",
+      testAllowedVersion('1.0.0', '1.1.0',
           nextVersionType: NextVersionType.MINOR);
     });
 
-    test("nextVersion does not allow skipping minor versions", () {
-      testAllowedVersion("1.0.1", "1.2.0", allowed: false);
-      testAllowedVersion("1.1.0", "1.3.0", allowed: false);
+    test('nextVersion does not allow skipping minor versions', () {
+      testAllowedVersion('1.0.1', '1.2.0', allowed: false);
+      testAllowedVersion('1.1.0', '1.3.0', allowed: false);
     });
 
-    test("nextVersion allows breaking changes", () {
-      testAllowedVersion("1.0.1", "2.0.0",
+    test('nextVersion allows breaking changes', () {
+      testAllowedVersion('1.0.1', '2.0.0',
           nextVersionType: NextVersionType.BREAKING_MAJOR);
-      testAllowedVersion("1.0.0", "2.0.0",
+      testAllowedVersion('1.0.0', '2.0.0',
           nextVersionType: NextVersionType.BREAKING_MAJOR);
     });
 
-    test("nextVersion allows null safety pre prelease", () {
-      testAllowedVersion("1.0.1", "2.0.0-nullsafety",
-          nextVersionType: NextVersionType.MAJOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("1.0.0", "2.0.0-nullsafety",
-          nextVersionType: NextVersionType.MAJOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("1.0.0-nullsafety", "1.0.0-nullsafety.1",
-          nextVersionType: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("1.0.0-nullsafety.1", "1.0.0-nullsafety.2",
-          nextVersionType: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("0.1.0", "0.2.0-nullsafety",
-          nextVersionType: NextVersionType.MAJOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("0.1.0-nullsafety", "0.1.0-nullsafety.1",
-          nextVersionType: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("0.1.0-nullsafety.1", "0.1.0-nullsafety.2",
-          nextVersionType: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("1.0.0", "1.1.0-nullsafety",
-          nextVersionType: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("1.1.0-nullsafety", "1.1.0-nullsafety.1",
-          nextVersionType: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("0.1.0", "0.1.1-nullsafety",
-          nextVersionType: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE);
-      testAllowedVersion("0.1.1-nullsafety", "0.1.1-nullsafety.1",
-          nextVersionType: NextVersionType.MINOR_NULLSAFETY_PRE_RELEASE);
-    });
-
-    test("nextVersion does not allow skipping major versions", () {
-      testAllowedVersion("1.0.1", "3.0.0", allowed: false);
-      testAllowedVersion("1.1.0", "2.3.0", allowed: false);
+    test('nextVersion does not allow skipping major versions', () {
+      testAllowedVersion('1.0.1', '3.0.0', allowed: false);
+      testAllowedVersion('1.1.0', '2.3.0', allowed: false);
     });
   });
 }
diff --git a/script/tool/test/xctest_command_test.dart b/script/tool/test/xctest_command_test.dart
index aa71c25835c8..1707dc8cfb8d 100644
--- a/script/tool/test/xctest_command_test.dart
+++ b/script/tool/test/xctest_command_test.dart
@@ -12,67 +12,67 @@ import 'package:test/test.dart';
 import 'mocks.dart';
 import 'util.dart';
 
-final _kDeviceListMap = {
-  "runtimes": [
-    {
-      "bundlePath":
-          "/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 13.0.simruntime",
-      "buildversion": "17A577",
-      "runtimeRoot":
-          "/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 13.0.simruntime/Contents/Resources/RuntimeRoot",
-      "identifier": "com.apple.CoreSimulator.SimRuntime.iOS-13-0",
-      "version": "13.0",
-      "isAvailable": true,
-      "name": "iOS 13.0"
+final Map<String, dynamic> _kDeviceListMap = <String, dynamic>{
+  'runtimes': <Map<String, dynamic>>[
+    <String, dynamic>{
+      'bundlePath':
+          '/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 13.0.simruntime',
+      'buildversion': '17A577',
+      'runtimeRoot':
+          '/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 13.0.simruntime/Contents/Resources/RuntimeRoot',
+      'identifier': 'com.apple.CoreSimulator.SimRuntime.iOS-13-0',
+      'version': '13.0',
+      'isAvailable': true,
+      'name': 'iOS 13.0'
     },
-    {
-      "bundlePath":
-          "/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 13.4.simruntime",
-      "buildversion": "17L255",
-      "runtimeRoot":
-          "/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 13.4.simruntime/Contents/Resources/RuntimeRoot",
-      "identifier": "com.apple.CoreSimulator.SimRuntime.iOS-13-4",
-      "version": "13.4",
-      "isAvailable": true,
-      "name": "iOS 13.4"
+    <String, dynamic>{
+      'bundlePath':
+          '/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 13.4.simruntime',
+      'buildversion': '17L255',
+      'runtimeRoot':
+          '/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 13.4.simruntime/Contents/Resources/RuntimeRoot',
+      'identifier': 'com.apple.CoreSimulator.SimRuntime.iOS-13-4',
+      'version': '13.4',
+      'isAvailable': true,
+      'name': 'iOS 13.4'
     },
-    {
-      "bundlePath":
-          "/Applications/Xcode_11_7.app/Contents/Developer/Platforms/WatchOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/watchOS.simruntime",
-      "buildversion": "17T531",
-      "runtimeRoot":
-          "/Applications/Xcode_11_7.app/Contents/Developer/Platforms/WatchOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/watchOS.simruntime/Contents/Resources/RuntimeRoot",
-      "identifier": "com.apple.CoreSimulator.SimRuntime.watchOS-6-2",
-      "version": "6.2.1",
-      "isAvailable": true,
-      "name": "watchOS 6.2"
+    <String, dynamic>{
+      'bundlePath':
+          '/Applications/Xcode_11_7.app/Contents/Developer/Platforms/WatchOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/watchOS.simruntime',
+      'buildversion': '17T531',
+      'runtimeRoot':
+          '/Applications/Xcode_11_7.app/Contents/Developer/Platforms/WatchOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/watchOS.simruntime/Contents/Resources/RuntimeRoot',
+      'identifier': 'com.apple.CoreSimulator.SimRuntime.watchOS-6-2',
+      'version': '6.2.1',
+      'isAvailable': true,
+      'name': 'watchOS 6.2'
     }
   ],
-  "devices": {
-    "com.apple.CoreSimulator.SimRuntime.iOS-13-4": [
-      {
-        "dataPath":
-            "/Users/xxx/Library/Developer/CoreSimulator/Devices/2706BBEB-1E01-403E-A8E9-70E8E5A24774/data",
-        "logPath":
-            "/Users/xxx/Library/Logs/CoreSimulator/2706BBEB-1E01-403E-A8E9-70E8E5A24774",
-        "udid": "2706BBEB-1E01-403E-A8E9-70E8E5A24774",
-        "isAvailable": true,
-        "deviceTypeIdentifier":
-            "com.apple.CoreSimulator.SimDeviceType.iPhone-8",
-        "state": "Shutdown",
-        "name": "iPhone 8"
+  'devices': <String, dynamic>{
+    'com.apple.CoreSimulator.SimRuntime.iOS-13-4': <Map<String, dynamic>>[
+      <String, dynamic>{
+        'dataPath':
+            '/Users/xxx/Library/Developer/CoreSimulator/Devices/2706BBEB-1E01-403E-A8E9-70E8E5A24774/data',
+        'logPath':
+            '/Users/xxx/Library/Logs/CoreSimulator/2706BBEB-1E01-403E-A8E9-70E8E5A24774',
+        'udid': '2706BBEB-1E01-403E-A8E9-70E8E5A24774',
+        'isAvailable': true,
+        'deviceTypeIdentifier':
+            'com.apple.CoreSimulator.SimDeviceType.iPhone-8',
+        'state': 'Shutdown',
+        'name': 'iPhone 8'
       },
-      {
-        "dataPath":
-            "/Users/xxx/Library/Developer/CoreSimulator/Devices/1E76A0FD-38AC-4537-A989-EA639D7D012A/data",
-        "logPath":
-            "/Users/xxx/Library/Logs/CoreSimulator/1E76A0FD-38AC-4537-A989-EA639D7D012A",
-        "udid": "1E76A0FD-38AC-4537-A989-EA639D7D012A",
-        "isAvailable": true,
-        "deviceTypeIdentifier":
-            "com.apple.CoreSimulator.SimDeviceType.iPhone-8-Plus",
-        "state": "Shutdown",
-        "name": "iPhone 8 Plus"
+      <String, dynamic>{
+        'dataPath':
+            '/Users/xxx/Library/Developer/CoreSimulator/Devices/1E76A0FD-38AC-4537-A989-EA639D7D012A/data',
+        'logPath':
+            '/Users/xxx/Library/Logs/CoreSimulator/1E76A0FD-38AC-4537-A989-EA639D7D012A',
+        'udid': '1E76A0FD-38AC-4537-A989-EA639D7D012A',
+        'isAvailable': true,
+        'deviceTypeIdentifier':
+            'com.apple.CoreSimulator.SimDeviceType.iPhone-8-Plus',
+        'state': 'Shutdown',
+        'name': 'iPhone 8 Plus'
       }
     ]
   }
@@ -83,7 +83,7 @@ void main() {
   const String _kSkip = '--skip';
 
   group('test xctest_command', () {
-    CommandRunner<Null> runner;
+    CommandRunner<void> runner;
     RecordingProcessRunner processRunner;
 
     setUp(() {
@@ -93,7 +93,7 @@ void main() {
           mockPackagesDir, mockFileSystem,
           processRunner: processRunner);
 
-      runner = CommandRunner<Null>('xctest_command', 'Test for xctest_command');
+      runner = CommandRunner<void>('xctest_command', 'Test for xctest_command');
       runner.addCommand(command);
       cleanupPackages();
     });
@@ -113,19 +113,15 @@ void main() {
       final MockProcess mockProcess = MockProcess();
       mockProcess.exitCodeCompleter.complete(0);
       processRunner.processToReturn = mockProcess;
-      final List<String> output = await runCapturingPrint(runner, <String>[
-        'xctest',
-        _kDestination,
-        'foo_destination'
-      ]);
+      final List<String> output = await runCapturingPrint(
+          runner, <String>['xctest', _kDestination, 'foo_destination']);
       expect(output, contains('iOS is not supported by this plugin.'));
       expect(processRunner.recordedCalls, orderedEquals(<ProcessCall>[]));
 
       cleanupPackages();
     });
 
-    test('running with correct destination, skip 1 plugin',
-        () async {
+    test('running with correct destination, skip 1 plugin', () async {
       createFakePlugin('plugin1',
           withExtraFiles: <List<String>>[
             <String>['example', 'test'],
@@ -149,7 +145,7 @@ void main() {
       processRunner.processToReturn = mockProcess;
       processRunner.resultStdout =
           '{"project":{"targets":["bar_scheme", "foo_scheme"]}}';
-      List<String> output = await runCapturingPrint(runner, <String>[
+      final List<String> output = await runCapturingPrint(runner, <String>[
         'xctest',
         _kDestination,
         'foo_destination',
@@ -165,7 +161,7 @@ void main() {
           orderedEquals(<ProcessCall>[
             ProcessCall(
                 'xcrun',
-                <String>[
+                const <String>[
                   'xcodebuild',
                   'test',
                   'analyze',
@@ -203,9 +199,9 @@ void main() {
       final MockProcess mockProcess = MockProcess();
       mockProcess.exitCodeCompleter.complete(0);
       processRunner.processToReturn = mockProcess;
-      final Map<String, dynamic> schemeCommandResult = {
-        "project": {
-          "targets": ["bar_scheme", "foo_scheme"]
+      final Map<String, dynamic> schemeCommandResult = <String, dynamic>{
+        'project': <String, dynamic>{
+          'targets': <String>['bar_scheme', 'foo_scheme']
         }
       };
       // For simplicity of the test, we combine all the mock results into a single mock result, each internal command
@@ -219,10 +215,11 @@ void main() {
       expect(
           processRunner.recordedCalls,
           orderedEquals(<ProcessCall>[
-            ProcessCall('xcrun', <String>['simctl', 'list', '--json'], null),
+            const ProcessCall(
+                'xcrun', <String>['simctl', 'list', '--json'], null),
             ProcessCall(
                 'xcrun',
-                <String>[
+                const <String>[
                   'xcodebuild',
                   'test',
                   'analyze',