feat: create max-expects rule (#1166)

* feat: create max-expects * fix: fix test * chore: update README * fix: set proper minimum * refactor: remove unnecessary functions * refactor: reduce if * refactor: remove unnecessary type check * fix: incorrect error reported in case of multiple test blocks * chore: typo * refactor: remove unnecessary type check * chore: remove unneeded return Co-authored-by: Gareth Jones <[email protected]>
jest-community · Jul 14, 2022 · 5b6fd20 · 5b6fd20
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diff --git a/README.md b/README.md
@@ -201,6 +201,7 @@ installations requiring long-term consistency.
 | ---------------------------------------------------------------------------- | ------------------------------------------------------------------- | ---------------- | ------------ |
 | [consistent-test-it](docs/rules/consistent-test-it.md)                       | Have control over `test` and `it` usages                            |                  | ![fixable][] |
 | [expect-expect](docs/rules/expect-expect.md)                                 | Enforce assertion to be made in a test body                         | ![recommended][] |              |
+| [max-expects](docs/rules/max-expects.md)                                     | Enforces a maximum number assertion calls in a test body            |                  |              |
 | [max-nested-describe](docs/rules/max-nested-describe.md)                     | Enforces a maximum depth to nested describe calls                   |                  |              |
 | [no-alias-methods](docs/rules/no-alias-methods.md)                           | Disallow alias methods                                              | ![style][]       | ![fixable][] |
 | [no-commented-out-tests](docs/rules/no-commented-out-tests.md)               | Disallow commented out tests                                        | ![recommended][] |              |

diff --git a/docs/rules/max-expects.md b/docs/rules/max-expects.md
@@ -0,0 +1,74 @@
+# Enforces a maximum number assertion calls in a test body (`max-expects`)
+
+As more assertions are made, there is a possible tendency for the test to be
+more likely to mix multiple objectives. To avoid this, this rule reports when
+the maximum number of assertions is exceeded.
+
+## Rule Details
+
+This rule enforces a maximum number of `expect()` calls.
+
+The following patterns are considered warnings (with the default option of
+`{ "max": 5 } `):
+
+```js
+test('should not pass', () => {
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+});
+
+it('should not pass', () => {
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+});
+```
+
+The following patterns are **not** considered warnings (with the default option
+of `{ "max": 5 } `):
+
+```js
+test('shout pass');
+
+test('shout pass', () => {});
+
+test.skip('shout pass', () => {});
+
+test('should pass', function () {
+  expect(true).toBeDefined();
+});
+
+test('should pass', () => {
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+});
+```
+
+## Options
+
+```json
+{
+  "jest/max-expects": [
+    "error",
+    {
+      "max": 5
+    }
+  ]
+}
+```
+
+### `max`
+
+Enforces a maximum number of `expect()`.
+
+This has a default value of `5`.
diff --git a/src/__tests__/__snapshots__/rules.test.ts.snap b/src/__tests__/__snapshots__/rules.test.ts.snap
@@ -12,6 +12,7 @@ Object {
     "rules": Object {
       "jest/consistent-test-it": "error",
       "jest/expect-expect": "error",
+      "jest/max-expects": "error",
       "jest/max-nested-describe": "error",
       "jest/no-alias-methods": "error",
       "jest/no-commented-out-tests": "error",

diff --git a/src/__tests__/rules.test.ts b/src/__tests__/rules.test.ts
@@ -2,7 +2,7 @@ import { existsSync } from 'fs';
 import { resolve } from 'path';
 import plugin from '../';
 
-const numberOfRules = 48;
+const numberOfRules = 49;
 const ruleNames = Object.keys(plugin.rules);
 const deprecatedRules = Object.entries(plugin.rules)
   .filter(([, rule]) => rule.meta.deprecated)

diff --git a/src/rules/__tests__/max-expects.test.ts b/src/rules/__tests__/max-expects.test.ts
@@ -0,0 +1,284 @@
+import { TSESLint } from '@typescript-eslint/utils';
+import dedent from 'dedent';
+import rule from '../max-expects';
+import { espreeParser } from './test-utils';
+
+const ruleTester = new TSESLint.RuleTester({
+  parser: espreeParser,
+  parserOptions: {
+    ecmaVersion: 2017,
+  },
+});
+
+ruleTester.run('max-expects', rule, {
+  valid: [
+    `test('should pass')`,
+    `test('should pass', () => {})`,
+    `test.skip('should pass', () => {})`,
+    dedent`
+      test('should pass', function () {
+        expect(true).toBeDefined();
+      });
+    `,
+    dedent`
+      test('should pass', () => {
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+      });
+    `,
+    dedent`
+      test('should pass', () => {
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        // expect(true).toBeDefined();
+      });
+    `,
+    dedent`
+      it('should pass', () => {
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+      });
+    `,
+    dedent`
+      test('should pass', async () => {
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+      });
+    `,
+    dedent`
+      describe('test', () => {
+        test('should pass', () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      });
+    `,
+    dedent`
+      test.each(['should', 'pass'], () => {
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+      });
+    `,
+    dedent`
+      test('should pass', () => {
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+      });
+      test('should pass', () => {
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+        expect(true).toBeDefined();
+      });
+    `,
+    {
+      code: dedent`
+        test('should pass', () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      `,
+      options: [
+        {
+          max: 10,
+        },
+      ],
+    },
+  ],
+  invalid: [
+    {
+      code: dedent`
+        test('should not pass', function () {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      `,
+      errors: [
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 7,
+          column: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        test('should not pass', () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      `,
+      errors: [
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 7,
+          column: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        it('should not pass', () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      `,
+      errors: [
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 7,
+          column: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        it('should not pass', async () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      `,
+      errors: [
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 7,
+          column: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        test('should not pass', () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+        test('should not pass', () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      `,
+      errors: [
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 7,
+          column: 3,
+        },
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 15,
+          column: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        describe('test', () => {
+          test('should not pass', () => {
+            expect(true).toBeDefined();
+            expect(true).toBeDefined();
+            expect(true).toBeDefined();
+            expect(true).toBeDefined();
+            expect(true).toBeDefined();
+            expect(true).toBeDefined();
+          });
+        });
+      `,
+      errors: [
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 8,
+          column: 5,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        test.each(['should', 'not', 'pass'], () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      `,
+      errors: [
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 7,
+          column: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        test('should not pass', () => {
+          expect(true).toBeDefined();
+          expect(true).toBeDefined();
+        });
+      `,
+      options: [
+        {
+          max: 1,
+        },
+      ],
+      errors: [
+        {
+          messageId: 'exceededMaxAssertion',
+          line: 3,
+          column: 3,
+        },
+      ],
+    },
+  ],
+});