Add test-title-format rule

docs/rules/test-title-format.md

@@ -0,0 +1,69 @@
+# Enforce test titles have a certain format
+
+This rule is useful when you want to make sure all test titles match a common pattern to increase readability when tests fail.
+
+For example, titles like `'Should throw when invalid.'`, `'Should fail when called.'` or `'Should pass when using any number.'` could be enforced with the following pattern `'^Should (pass|fail|throw) when [\\w ]+\\.$'` (Note the escaped `\`).
+
+
+## Fail
+
+```js
+/* eslint ava/test-title: ["error", {format: "^Should"}] */
+import test from 'ava';
+
+test('Not starting with `Should`', t => {
+	t.pass();
+});
+```
+
+```js
+/* eslint ava/test-title: ["error", {format: "\\.$"}] */
+import test from 'ava';
+
+test('Doesn\'t end with a dot', t => {
+	t.pass();
+});
+```
+
+
+## Pass
+
+```js
+/* eslint ava/test-title: ["error", {format: "^Should"}] */
+import test from 'ava';
+
+test('Should pass tests', t => {
+	t.pass();
+});
+
+test('Should behave as expected', t => {
+	t.pass();
+});
+```
+
+```js
+/* eslint ava/test-title: ["error", {format: "\\.$"}] */
+import test from 'ava';
+
+test('End with a dot.', t => {
+	t.pass();
+});
+```
+
+
+## Options
+
+This rule supports the following options:
+
+`format`: A regular expression string to match against the test titles.
+
+You can set the options like this:
+
+```json
+"ava/test-title-format": [
+	"error",
+	{
+		"format": "^Should"
+	}
+]
+```

index.js

@@ -44,6 +44,7 @@ module.exports = {
 					'error',
 					'if-multiple'
 				],
+				'ava/test-title-format': 'off',
 				'ava/use-t-well': 'error',
 				'ava/use-t': 'error',
 				'ava/use-test': 'error',

readme.md

@@ -60,6 +60,7 @@ Configure it in `package.json`.
 				"error",
 				"if-multiple"
 			],
+			"ava/test-title-format": "off",
 			"ava/use-t-well": "error",
 			"ava/use-t": "error",
 			"ava/use-test": "error",
@@ -95,6 +96,7 @@ The rules will only activate in test files.
 - [prefer-power-assert](docs/rules/prefer-power-assert.md) - Allow only use of the asserts that have no [power-assert](https://github.com/power-assert-js/power-assert) alternative.
 - [test-ended](docs/rules/test-ended.md) - Ensure callback tests are explicitly ended.
 - [test-title](docs/rules/test-title.md) - Ensure tests have a title.
+- [test-title-format](docs/rules/test-title-format.md) - Ensure tests have a correct title format.
 - [use-t-well](docs/rules/use-t-well.md) - Prevent the incorrect use of `t`.
 - [use-t](docs/rules/use-t.md) - Ensure test functions use `t` as their parameter.
 - [use-test](docs/rules/use-test.md) - Ensure that AVA is imported with `test` as the variable name.

rules/test-title-format.js

@@ -0,0 +1,46 @@
+'use strict';
+const {visitIf} = require('enhance-visitors');
+const createAvaRule = require('../create-ava-rule');
+const util = require('../util');
+
+const create = context => {
+	const ava = createAvaRule();
+
+	let titleRegExp;
+	if (context.options[0] && context.options[0].format) {
+		titleRegExp = new RegExp(context.options[0].format);
+	} else {
+		return {};
+	}
+
+	return ava.merge({
+		CallExpression: visitIf([
+			ava.isInTestFile,
+			ava.isTestNode,
+			ava.hasNoHookModifier
+		])(node => {
+			const requiredLength = ava.hasTestModifier('todo') ? 1 : 2;
+			const hasTitle = node.arguments.length >= requiredLength;
+
+			if (hasTitle) {
+				const title = node.arguments[0];
+				if (title.type === 'Literal' && !titleRegExp.test(title.value)) {
+					context.report({
+						node,
+						message: `The test title doesn't match the required format: ${titleRegExp}`
+					});
+				}
+			}
+		})
+	});
+};
+
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			url: util.getDocsUrl(__filename)
+		}
+	}
+};

test/test-title-format.js

@@ -0,0 +1,59 @@
+import test from 'ava';
+import avaRuleTester from 'eslint-ava-rule-tester';
+import rule from '../rules/test-title-format';
+
+const ruleTester = avaRuleTester(test, {
+	env: {
+		es6: true
+	}
+});
+
+const errors = [{ruleId: 'test-title-format'}];
+const header = 'const test = require(\'ava\');\n';
+
+ruleTester.run('test-title-format', rule, {
+	valid: [
+		header + 'test("Foo", t => { t.pass(); });',
+		{
+			code: header + 'test("Foo", t => { t.pass(); });',
+			options: [{format: '.'}]
+		},
+		{
+			code: header + 'test("Should pass tests.", t => { t.pass(); });',
+			options: [{format: '^Should .+\\.$'}]
+		},
+		{
+			code: header + 'test.todo("Should pass tests.");',
+			options: [{format: '^Should .+\\.$'}]
+		},
+		{
+			code: header + 'test(t => { t.pass(); });',
+			options: [{format: '^Should'}]
+		},
+		{
+			code: header + 'notTest("Foo", t => { t.pass(); });',
+			options: [{format: '^Should'}]
+		},
+		{
+			code: header + 'test(macro, t => { t.pass(); });',
+			options: [{format: '^Should'}]
+		},
+		// Shouldn't be triggered since it's not a test file
+		{
+			code: 'test("Test", t => { t.pass(); });',
+			options: [{format: '^Should'}]
+		}
+	],
+	invalid: [
+		{
+			code: header + 'test("Test something", t => { t.pass(); });',
+			options: [{format: '^Should'}],
+			errors
+		},
+		{
+			code: header + 'test.todo("Test something");',
+			options: [{format: '^Should'}],
+			errors
+		}
+	]
+});