feat: add prefer-to-contain rule (#174)

Fixes #100

README.md

@@ -97,6 +97,7 @@ for more information about extending configuration files.
 | [prefer-strict-equal][]      | Suggest using `toStrictEqual()`                                   |                  | ![fixable-green][]  |
 | [prefer-to-be-null][]        | Suggest using `toBeNull()`                                        |                  | ![fixable-green][]  |
 | [prefer-to-be-undefined][]   | Suggest using `toBeUndefined()`                                   |                  | ![fixable-green][]  |
+| [prefer-to-contain][]        | Suggest using `toContain()`                                       |                  | ![fixable-green][]  |
 | [prefer-to-have-length][]    | Suggest using `toHaveLength()`                                    | ![recommended][] | ![fixable-green][]  |
 | [prefer-inline-snapshots][]  | Suggest using `toMatchInlineSnapshot()`                           |                  | ![fixable-green][]  |
 | [require-tothrow-message][]  | Require that `toThrow()` and `toThrowError` includes a message    |                  |                     |
@@ -126,6 +127,7 @@ for more information about extending configuration files.
 [prefer-strict-equal]: docs/rules/prefer-strict-equal.md
 [prefer-to-be-null]: docs/rules/prefer-to-be-null.md
 [prefer-to-be-undefined]: docs/rules/prefer-to-be-undefined.md
+[prefer-to-contain]: docs/rules/prefer-to-contain.md
 [prefer-to-have-length]: docs/rules/prefer-to-have-length.md
 [prefer-inline-snapshots]: docs/rules/prefer-inline-snapshots.md
 [require-tothrow-message]: docs/rules/require-tothrow-message.md

docs/rules/prefer-to-contain.md

@@ -0,0 +1,47 @@
+# Suggest using `toContain()` (prefer-to-contain)
+
+In order to have a better failure message, `toContain()` should be used upon
+asserting expectations on an array containing an object.
+
+## Rule details
+
+This rule triggers a warning if `toBe()` or `isEqual()` is used to assert object
+inclusion in an array
+
+```js
+expect(a.includes(b)).toBe(true);
+```
+
+```js
+expect(a.includes(b)).not.toBe(true);
+```
+
+```js
+expect(a.includes(b)).toBe(false);
+```
+
+### Default configuration
+
+The following patterns are considered a warning:
+
+```js
+expect(a.includes(b)).toBe(true);
+```
+
+```js
+expect(a.includes(b)).not.toBe(true);
+```
+
+```js
+expect(a.includes(b)).toBe(false);
+```
+
+The following patterns are not a warning:
+
+```js
+expect(a).toContain(b);
+```
+
+```js
+expect(a).not.toContain(b);
+```

index.js

@@ -14,6 +14,7 @@ const noTestPrefixes = require('./rules/no-test-prefixes');
 const noTestReturnStatement = require('./rules/no-test-return-statement');
 const preferToBeNull = require('./rules/prefer-to-be-null');
 const preferToBeUndefined = require('./rules/prefer-to-be-undefined');
+const preferToContain = require('./rules/prefer-to-contain');
 const preferToHaveLength = require('./rules/prefer-to-have-length');
 const validDescribe = require('./rules/valid-describe');
 const validExpect = require('./rules/valid-expect');
@@ -84,6 +85,7 @@ module.exports = {
     'no-test-return-statement': noTestReturnStatement,
     'prefer-to-be-null': preferToBeNull,
     'prefer-to-be-undefined': preferToBeUndefined,
+    'prefer-to-contain': preferToContain,
     'prefer-to-have-length': preferToHaveLength,
     'valid-describe': validDescribe,
     'valid-expect': validExpect,

rules/__tests__/prefer-to-contain.test.js

@@ -0,0 +1,207 @@
+'use strict';
+
+const RuleTester = require('eslint').RuleTester;
+const rule = require('../prefer-to-contain');
+
+const ruleTester = new RuleTester();
+
+ruleTester.run('prefer-to-contain', rule, {
+  valid: [
+    'expect(a).toContain(b);',
+    "expect(a.name).toBe('b');",
+    'expect(a).toBe(true);',
+    `expect(a).toEqual(b)`,
+    `expect(a.test(c)).toEqual(b)`,
+    `expect(a.includes(b)).toEqual()`,
+    `expect(a.includes(b)).toEqual("test")`,
+    `expect(a.includes(b)).toBe("test")`,
+    `expect(a.includes()).toEqual()`,
+    `expect(a.includes()).toEqual(true)`,
+    `expect(a.includes(b,c)).toBe(true)`,
+    `expect([{a:1}]).toContain({a:1})`,
+    `expect([1].includes(1)).toEqual`,
+    `expect([1].includes).toEqual`,
+    `expect([1].includes).not`,
+    `expect(a.test(b)).resolves.toEqual(true)`,
+    `expect(a.test(b)).resolves.not.toEqual(true)`,
+    `expect(a).not.toContain(b)`,
+  ],
+  invalid: [
+    {
+      code: 'expect(a.includes(b)).toEqual(true);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 23,
+          line: 1,
+        },
+      ],
+      output: 'expect(a).toContain(b);',
+    },
+    {
+      code: 'expect(a.includes(b)).toEqual(false);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 23,
+          line: 1,
+        },
+      ],
+      output: 'expect(a).not.toContain(b);',
+    },
+    {
+      code: 'expect(a.includes(b)).not.toEqual(false);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 23,
+          line: 1,
+        },
+      ],
+      output: 'expect(a).toContain(b);',
+    },
+    {
+      code: 'expect(a.includes(b)).not.toEqual(true);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 23,
+          line: 1,
+        },
+      ],
+      output: 'expect(a).not.toContain(b);',
+    },
+    {
+      code: 'expect(a.includes(b)).toBe(true);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 23,
+          line: 1,
+        },
+      ],
+      output: 'expect(a).toContain(b);',
+    },
+    {
+      code: 'expect(a.includes(b)).toBe(false);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 23,
+          line: 1,
+        },
+      ],
+      output: 'expect(a).not.toContain(b);',
+    },
+    {
+      code: 'expect(a.includes(b)).not.toBe(false);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 23,
+          line: 1,
+        },
+      ],
+      output: 'expect(a).toContain(b);',
+    },
+    {
+      code: 'expect(a.includes(b)).not.toBe(true);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 23,
+          line: 1,
+        },
+      ],
+      output: 'expect(a).not.toContain(b);',
+    },
+    {
+      code: 'expect(a.test(t).includes(b.test(p))).toEqual(true);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 39,
+          line: 1,
+        },
+      ],
+      output: 'expect(a.test(t)).toContain(b.test(p));',
+    },
+    {
+      code: 'expect(a.test(t).includes(b.test(p))).toEqual(false);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 39,
+          line: 1,
+        },
+      ],
+      output: 'expect(a.test(t)).not.toContain(b.test(p));',
+    },
+    {
+      code: 'expect(a.test(t).includes(b.test(p))).not.toEqual(true);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 39,
+          line: 1,
+        },
+      ],
+      output: 'expect(a.test(t)).not.toContain(b.test(p));',
+    },
+    {
+      code: 'expect(a.test(t).includes(b.test(p))).not.toEqual(false);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 39,
+          line: 1,
+        },
+      ],
+      output: 'expect(a.test(t)).toContain(b.test(p));',
+    },
+    {
+      code: 'expect([{a:1}].includes({a:1})).toBe(true);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 33,
+          line: 1,
+        },
+      ],
+      output: 'expect([{a:1}]).toContain({a:1});',
+    },
+    {
+      code: 'expect([{a:1}].includes({a:1})).toBe(false);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 33,
+          line: 1,
+        },
+      ],
+      output: 'expect([{a:1}]).not.toContain({a:1});',
+    },
+    {
+      code: 'expect([{a:1}].includes({a:1})).not.toBe(true);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 33,
+          line: 1,
+        },
+      ],
+      output: 'expect([{a:1}]).not.toContain({a:1});',
+    },
+    {
+      code: 'expect([{a:1}].includes({a:1})).not.toBe(false);',
+      errors: [
+        {
+          message: 'Use toContain() instead',
+          column: 33,
+          line: 1,
+        },
+      ],
+      output: 'expect([{a:1}]).toContain({a:1});',
+    },
+  ],
+});