New: no-identical-tests rule (#11)

Author: aladdin-add

README.md

@@ -56,6 +56,7 @@ Name | ✔️ | 🛠 | Description
 [prefer-placeholders](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/prefer-placeholders.md) | | | Disallows template literals as report messages
 [no-useless-token-range](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/no-useless-token-range.md) | ✔️ | 🛠 | Disallows unnecessary calls to sourceCode.getFirstToken and sourceCode.getLastToken
 [consistent-output](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/consistent-output.md) | | | Enforces consistent use of output assertions in rule tests
+[no-identical-tests](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/no-identical-tests.md) | | | Disallows identical tests
 
 ## Supported Presets
 

docs/rules/no-identical-tests.md

@@ -0,0 +1,39 @@
+# Disallow identical tests (no-identical-tests)
+
+When a rule has a lot of tests, it's sometimes difficult to tell if any tests are duplicates. This rule would warn if any test cases have the same properties.
+
+## Rule Details
+
+Examples of **incorrect** code for this rule:
+
+```js
+/* eslint eslint-plugin/no-identical-tests: error */
+
+new RuleTester().run('foo', bar, {
+valid: [
+    { code: 'foo' },
+    { code: 'foo' }
+],
+invalid: []
+});
+
+```
+
+Examples of **correct** code for this rule:
+
+```js
+/* eslint eslint-plugin/no-identical-tests: error */
+
+new RuleTester().run('foo', bar, {
+valid: [
+    { code: 'foo' },
+    { code: 'bar' }
+],
+invalid: []
+});
+
+```
+
+## When Not To Use It
+
+If you want to allow identical tests, do not enable this rule.

lib/rules/no-identical-tests.js

@@ -0,0 +1,54 @@
+/**
+ * @fileoverview disallow identical tests
+ * @author 薛定谔的猫<[email protected]>
+ */
+
+'use strict';
+
+const utils = require('../utils');
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'disallow identical tests',
+      category: 'Tests',
+      recommended: false,
+    },
+    fixable: null,  // or "code" or "whitespace"
+    schema: [],
+  },
+
+  create (context) {
+    // ----------------------------------------------------------------------
+    // Public
+    // ----------------------------------------------------------------------
+    const message = 'This test case is identical to another case.';
+    const sourceCode = context.getSourceCode();
+
+    return {
+      Program (ast) {
+        utils.getTestInfo(context, ast).forEach(testRun => {
+          [testRun.valid, testRun.invalid].forEach(tests => {
+            const cache = Object.create(null);
+            // to avoid tests being null
+            (tests || []).forEach(test => {
+              const testCode = sourceCode.getText(test);
+              if (cache[testCode]) {
+                context.report({
+                  node: test,
+                  message,
+                });
+              } else {
+                cache[testCode] = true;
+              }
+            });
+          });
+        });
+      },
+    };
+  },
+};

tests/lib/rules/no-identical-tests.js

@@ -0,0 +1,64 @@
+/**
+ * @fileoverview disallow identical tests
+ * @author 薛定谔的猫<[email protected]>
+ */
+
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const rule = require('../../../lib/rules/no-identical-tests');
+const RuleTester = require('eslint').RuleTester;
+
+const ERROR = { message: 'This test case is identical to another case.' };
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester();
+ruleTester.run('no-identical-tests', rule, {
+  valid: [
+    `
+      new RuleTester().run('foo', bar, {
+        valid: [
+          { code: 'foo' },
+          { code: 'bar' }
+        ],
+        invalid: []
+      });
+    `,
+  ],
+
+  invalid: [
+    {
+      code: `
+        new RuleTester().run('foo', bar, {
+          valid: [
+            { code: 'foo' },
+            { code: 'foo' }
+          ],
+          invalid: []
+        });
+      `,
+      errors: [ERROR],
+    },
+    {
+      code: `
+        new RuleTester().run('foo', bar, {
+          valid: [
+            { code: 'foo' },
+            { code: 'foo' },
+          ],
+          invalid: [
+            { code: 'foo', errors: ['bar'] },
+            { code: 'foo', errors: ['bar'] },
+          ]
+        });
+      `,
+      errors: [ERROR, ERROR],
+    },
+  ],
+});