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feat(prefer-mocked): add new rule (#1470)
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s.v.zaytsev committed May 30, 2024
1 parent 70c8c5e commit 9195234
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1 change: 1 addition & 0 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -352,6 +352,7 @@ set to warn in.\
| [prefer-importing-jest-globals](docs/rules/prefer-importing-jest-globals.md) | Prefer importing Jest globals | | | 🔧 | |
| [prefer-lowercase-title](docs/rules/prefer-lowercase-title.md) | Enforce lowercase test names | | | 🔧 | |
| [prefer-mock-promise-shorthand](docs/rules/prefer-mock-promise-shorthand.md) | Prefer mock resolved/rejected shorthands for promises | | | 🔧 | |
| [prefer-mocked](docs/rules/prefer-mocked.md) | Prefer jest.mocked() over (fn as jest.Mock) | | | 🔧 | |
| [prefer-snapshot-hint](docs/rules/prefer-snapshot-hint.md) | Prefer including a hint with external snapshots | | | | |
| [prefer-spy-on](docs/rules/prefer-spy-on.md) | Suggest using `jest.spyOn()` | | | 🔧 | |
| [prefer-strict-equal](docs/rules/prefer-strict-equal.md) | Suggest using `toStrictEqual()` | | | | 💡 |
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31 changes: 31 additions & 0 deletions docs/rules/prefer-mocked.md
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@@ -0,0 +1,31 @@
# Prefer jest.mocked() over (fn as jest.Mock) (`prefer-mocked`)

🔧 This rule is automatically fixable by the
[`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix).

<!-- end auto-generated rule header -->

When working with mocks of functions using Jest, it's recommended to use the
jest.mocked helper function to properly type the mocked functions. This rule
enforces the use of jest.mocked for better type safety and readability.

## Rule details

The following patterns are warnings:

```typescript
(foo as jest.Mock).mockReturnValue(1);
const mock = (foo as jest.Mock).mockReturnValue(1);
(foo as unknown as jest.Mock).mockReturnValue(1);
(Obj.foo as jest.Mock).mockReturnValue(1);
([].foo as jest.Mock).mockReturnValue(1);
```

The following patterns are not warnings:

```js
jest.mocked(foo).mockReturnValue(1);
const mock = jest.mocked(foo).mockReturnValue(1);
jest.mocked(Obj.foo).mockReturnValue(1);
jest.mocked([].foo).mockReturnValue(1);
```
2 changes: 2 additions & 0 deletions src/__tests__/__snapshots__/rules.test.ts.snap
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Expand Up @@ -48,6 +48,7 @@ exports[`rules should export configs that refer to actual rules 1`] = `
"jest/prefer-importing-jest-globals": "error",
"jest/prefer-lowercase-title": "error",
"jest/prefer-mock-promise-shorthand": "error",
"jest/prefer-mocked": "error",
"jest/prefer-snapshot-hint": "error",
"jest/prefer-spy-on": "error",
"jest/prefer-strict-equal": "error",
Expand Down Expand Up @@ -130,6 +131,7 @@ exports[`rules should export configs that refer to actual rules 1`] = `
"jest/prefer-importing-jest-globals": "error",
"jest/prefer-lowercase-title": "error",
"jest/prefer-mock-promise-shorthand": "error",
"jest/prefer-mocked": "error",
"jest/prefer-snapshot-hint": "error",
"jest/prefer-spy-on": "error",
"jest/prefer-strict-equal": "error",
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2 changes: 1 addition & 1 deletion src/__tests__/rules.test.ts
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Expand Up @@ -2,7 +2,7 @@ import { existsSync } from 'fs';
import { resolve } from 'path';
import plugin from '../';

const numberOfRules = 53;
const numberOfRules = 54;
const ruleNames = Object.keys(plugin.rules);
const deprecatedRules = Object.entries(plugin.rules)
.filter(([, rule]) => rule.meta.deprecated)
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321 changes: 321 additions & 0 deletions src/rules/__tests__/prefer-mocked.test.ts
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@@ -0,0 +1,321 @@
import path from 'path';
import dedent from 'dedent';
import rule from '../prefer-mocked';
import { FlatCompatRuleTester as RuleTester } from './test-utils';

function getFixturesRootDir(): string {
return path.join(__dirname, 'fixtures');
}

const rootPath = getFixturesRootDir();

const ruleTester = new RuleTester({
parser: require.resolve('@typescript-eslint/parser'),
parserOptions: {
sourceType: 'module',
tsconfigRootDir: rootPath,
project: './tsconfig.json',
},
});

ruleTester.run('prefer-mocked', rule, {
valid: [
dedent`
import { foo } from './foo';
foo();
`,

dedent`
import { foo } from './foo';
jest.mocked(foo).mockReturnValue(1);
`,

dedent`
import { bar } from './bar';
bar.mockReturnValue(1);
`,

dedent`
import { foo } from './foo';
sinon.stub(foo).returns(1);
`,

dedent`
import { foo } from './foo';
foo.mockImplementation(() => 1);
`,

dedent`
const obj = { foo() {} };
obj.foo();
`,

dedent`
const mockFn = jest.fn();
mockFn.mockReturnValue(1);
`,

dedent`
const arr = [() => {}];
arr[0]();
`,

dedent`
const obj = { foo() {} };
obj.foo.mockReturnValue(1);
`,

dedent`
const obj = { foo() {} };
jest.spyOn(obj, 'foo').mockReturnValue(1);
`,

dedent`
type MockType = jest.Mock;
const mockFn = jest.fn();
(mockFn as MockType).mockReturnValue(1);
`,
],
invalid: [
{
code: dedent`
import { foo } from './foo';
(foo as jest.Mock).mockReturnValue(1);
`,
output: dedent`
import { foo } from './foo';
(jest.mocked(foo)).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 3,
},
],
},
{
code: dedent`
import { foo } from './foo';
(foo as jest.Mock).mockImplementation(1);
`,
output: dedent`
import { foo } from './foo';
(jest.mocked(foo)).mockImplementation(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 3,
},
],
},
{
code: dedent`
import { foo } from './foo';
(foo as unknown as jest.Mock).mockReturnValue(1);
`,
output: dedent`
import { foo } from './foo';
(jest.mocked(foo)).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 3,
},
],
},
{
code: dedent`
import { Obj } from './foo';
(Obj.foo as jest.Mock).mockReturnValue(1);
`,
output: dedent`
import { Obj } from './foo';
(jest.mocked(Obj.foo)).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 3,
},
],
},
{
code: dedent`
([].foo as jest.Mock).mockReturnValue(1);
`,
output: dedent`
(jest.mocked([].foo)).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 1,
},
],
},
{
code: dedent`
import { foo } from './foo';
(foo as jest.MockedFunction).mockReturnValue(1);
`,
output: dedent`
import { foo } from './foo';
(jest.mocked(foo)).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 3,
},
],
},
{
code: dedent`
import { foo } from './foo';
(foo as jest.MockedFunction).mockImplementation(1);
`,
output: dedent`
import { foo } from './foo';
(jest.mocked(foo)).mockImplementation(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 3,
},
],
},
{
code: dedent`
import { foo } from './foo';
(foo as unknown as jest.MockedFunction).mockReturnValue(1);
`,
output: dedent`
import { foo } from './foo';
(jest.mocked(foo)).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 3,
},
],
},
{
code: dedent`
import { Obj } from './foo';
(Obj.foo as jest.MockedFunction).mockReturnValue(1);
`,
output: dedent`
import { Obj } from './foo';
(jest.mocked(Obj.foo)).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 3,
},
],
},
{
code: dedent`
(new Array(0).fill(null).foo as jest.MockedFunction).mockReturnValue(1);
`,
output: dedent`
(jest.mocked(new Array(0).fill(null).foo)).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 1,
},
],
},
{
code: dedent`
(jest.fn(() => foo) as jest.MockedFunction).mockReturnValue(1);
`,
output: dedent`
(jest.mocked(jest.fn(() => foo))).mockReturnValue(1);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 2,
line: 1,
},
],
},
{
code: dedent`
const mockedUseFocused = useFocused as jest.MockedFunction<typeof useFocused>;
`,
output: dedent`
const mockedUseFocused = jest.mocked(useFocused);
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 26,
line: 1,
},
],
},
{
code: dedent`
const filter = (MessageService.getMessage as jest.Mock).mock.calls[0][0];
`,
output: dedent`
const filter = (jest.mocked(MessageService.getMessage)).mock.calls[0][0];
`,
options: [],
errors: [
{
messageId: 'useJestMocked',
column: 17,
line: 1,
},
],
},
],
});
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