Add a matcher for Matrix4 that includes epsilon (#107326)

Author: jonahwilliams

packages/flutter_test/lib/src/matchers.dart

@@ -266,6 +266,18 @@ Matcher rectMoreOrLessEquals(Rect value, { double epsilon = precisionErrorTolera
   return _IsWithinDistance<Rect>(_rectDistance, value, epsilon);
 }
 
+/// Asserts that two [Matrix4]s are equal, within some tolerated error.
+///
+/// {@macro flutter.flutter_test.moreOrLessEquals}
+///
+/// See also:
+///
+///  * [moreOrLessEquals], which is for [double]s.
+///  * [offsetMoreOrLessEquals], which is for [Offset]s.
+Matcher matrixMoreOrLessEquals(Matrix4 value, { double epsilon = precisionErrorTolerance }) {
+  return _IsWithinDistance<Matrix4>(_matrixDistance, value, epsilon);
+}
+
 /// Asserts that two [Offset]s are equal, within some tolerated error.
 ///
 /// {@macro flutter.flutter_test.moreOrLessEquals}
@@ -1144,6 +1156,14 @@ double _rectDistance(Rect a, Rect b) {
   return delta;
 }
 
+double _matrixDistance(Matrix4 a, Matrix4 b) {
+  double delta = 0.0;
+  for (int i = 0; i < 16; i += 1) {
+    delta = math.max<double>((a[i] - b[i]).abs(), delta);
+  }
+  return delta;
+}
+
 double _sizeDistance(Size a, Size b) {
   // TODO(a14n): remove ignore when lint is updated, https://github.com/dart-lang/linter/issues/1843
   // ignore: unnecessary_parenthesis

packages/flutter_test/test/matchers_test.dart

@@ -4,6 +4,7 @@
 
 // flutter_ignore_for_file: golden_tag (see analyze.dart)
 
+import 'dart:math' as math;
 import 'dart:typed_data';
 
 import 'package:flutter/rendering.dart';
@@ -197,6 +198,38 @@ void main() {
     expect(-11.0, moreOrLessEquals(11.0, epsilon: 100.0));
   });
 
+  test('matrixMoreOrLessEquals', () {
+    expect(
+      Matrix4.rotationZ(math.pi),
+      matrixMoreOrLessEquals(Matrix4.fromList(<double>[
+       -1,  0, 0, 0,
+        0, -1, 0, 0,
+        0,  0, 1, 0,
+        0,  0, 0, 1,
+      ]))
+    );
+
+    expect(
+      Matrix4.rotationZ(math.pi),
+      matrixMoreOrLessEquals(Matrix4.fromList(<double>[
+       -2,  0, 0, 0,
+        0, -2, 0, 0,
+        0,  0, 1, 0,
+        0,  0, 0, 1,
+      ]), epsilon: 2)
+    );
+
+    expect(
+      Matrix4.rotationZ(math.pi),
+      isNot(matrixMoreOrLessEquals(Matrix4.fromList(<double>[
+       -2,  0, 0, 0,
+        0, -2, 0, 0,
+        0,  0, 1, 0,
+        0,  0, 0, 1,
+      ])))
+    );
+  });
+
   test('rectMoreOrLessEquals', () {
     expect(
       const Rect.fromLTRB(0.0, 0.0, 10.0, 10.0),