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Add new rule no-long-arrays-in-test-each (#3)
* Update wording * Add new rule `no-long-arrays-in-test-each` * Add docs
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‎README.md

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@@ -93,6 +93,7 @@ To enable this configuration with `.eslintrc`, use the `extends` property:
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| Name                             | Description | 💼 |
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| :--------------------------------------------------------------------------------- | :---------------------------------------------------------------------------------------- | :- |
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| [no-long-arrays-in-test-each](docs/rules/no-long-arrays-in-test-each.md) | Disallow mixing expectations for different variables between each other. | ✅ |
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| [no-mixed-expectation-groups](docs/rules/no-mixed-expectation-groups.md) | Disallow mixing expectations for different variables between each other. | ✅ |
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| [no-useless-matcher-to-be-defined](docs/rules/no-useless-matcher-to-be-defined.md) | Disallow using `.toBeDefined()` matcher when it is known that variable is always defined. | ✅ |
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| [no-useless-matcher-to-be-null](docs/rules/no-useless-matcher-to-be-null.md) | Disallow using `.toBeNull()` when TypeScript types conflict with it. | ✅ |

‎docs/rules/no-long-arrays-in-test-each.md

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# Disallow mixing expectations for different variables between each other (`proper-tests/no-long-arrays-in-test-each`)
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💼 This rule is enabled in the ✅ `recommended` config.
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<!-- end auto-generated rule header -->
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## Rule details
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This rule disallows mixing expectations for different variables between each other.
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The following code is considered errors:
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```ts
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test.each([
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{
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description: 'test case name #1',
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inputValue: 'a',
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expectedOutput: 'aa',
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},
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{
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description: 'test case name #2',
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inputValue: 'b',
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expectedOutput: 'bb',
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},
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{
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description: 'test case name #3',
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inputValue: 'c',
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expectedOutput: 'cc',
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},
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{
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description: 'test case name #4',
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inputValue: 'd',
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expectedOutput: 'dd',
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},
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{
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description: 'test case name #5',
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inputValue: 'e',
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expectedOutput: 'ee',
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},
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{
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description: 'test case name #6',
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inputValue: 'f',
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expectedOutput: 'ff',
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},
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])('$description', ({ clientCountry, expectedPaymentMethod, processorName }) => {
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// ...
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});
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```
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Consider extracting such long arrays to a separate files with for example `.data.ts` postfix.
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The following code is considered correct:
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```ts
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// some-service.data.ts
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export type TestCase = Readonly<{
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description: string;
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inputValue: string;
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expectedOutput: string;
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}>;
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export const testCases: TestCase[] = [
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{
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description: 'test case name #1',
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inputValue: 'a',
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expectedOutput: 'aa',
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},
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{
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description: 'test case name #2',
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inputValue: 'b',
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expectedOutput: 'bb',
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},
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{
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description: 'test case name #3',
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inputValue: 'c',
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expectedOutput: 'cc',
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},
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{
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description: 'test case name #4',
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inputValue: 'd',
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expectedOutput: 'dd',
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},
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{
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description: 'test case name #5',
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inputValue: 'e',
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expectedOutput: 'ee',
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},
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{
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description: 'test case name #6',
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inputValue: 'f',
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expectedOutput: 'ff',
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},
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];
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```
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and now test is more readable:
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```ts
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test.each(testCases)('$description', ({ inputValue, expectedOutput }) => {
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// ...
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});
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```

‎src/configs/recommended.ts

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'proper-tests/no-useless-matcher-to-be-defined': 'error',
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'proper-tests/no-useless-matcher-to-be-null': 'error',
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'proper-tests/no-mixed-expectation-groups': 'error',
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'proper-tests/no-long-arrays-in-test-each': 'error',
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},
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} satisfies ClassicConfig.Config;

‎src/custom-rules/no-long-arrays-in-test-each.spec.ts

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import { RuleTester } from '@typescript-eslint/rule-tester';
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import { noLongArraysInTestEach } from './no-long-arrays-in-test-each';
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const ruleTester = new RuleTester({
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parser: '@typescript-eslint/parser',
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});
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ruleTester.run('no-long-arrays-in-test-each', noLongArraysInTestEach, {
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valid: [
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{
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name: 'less than default limit using "test"',
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filename: 'app.e2e-spec.ts',
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code: `test.each([{}])`,
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},
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{
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name: 'less than default limit using "it"',
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filename: 'app.e2e-spec.ts',
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code: `it.each([{}])`,
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},
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{
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name: 'with integers using "test"',
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filename: 'app.e2e-spec.ts',
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code: 'test.each([1, 2, 3, 4, 5, 6]);',
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},
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{
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name: 'with integers using "it"',
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filename: 'app.e2e-spec.ts',
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code: 'it.each([1, 2, 3, 4, 5, 6]);',
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},
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{
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name: 'with mixed integers and objects using "it"',
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filename: 'app.e2e-spec.ts',
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code: 'it.each([{}, {}, {}, {}, {}, 1, 2, 3, 4, 5]);',
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},
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{
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name: 'with 6 objects when option is overridden using "it"',
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filename: 'app.e2e-spec.ts',
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options: [{ limit: 7 }],
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code: 'it.each([{}, {}, {}, {}, {}, {}]);',
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},
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{
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name: 'with 2 objects when option is overridden using "it"',
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filename: 'app.e2e-spec.ts',
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options: [{ limit: 4 }],
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code: 'it.each([{}, {}]);',
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},
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{
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name: 'string contains it.each',
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filename: 'app.e2e-spec.ts',
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code: '"it.each([{}, {}])";',
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},
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{
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name: 'simple function call is executed',
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filename: 'app.e2e-spec.ts',
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code: 'each([{}, {}]);',
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},
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{
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name: 'neither test nor it object is used',
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filename: 'app.e2e-spec.ts',
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code: 'array.each([{}, {}]);',
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},
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{
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name: 'called function is not "each"',
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filename: 'app.e2e-spec.ts',
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code: 'test.every([{}, {}]);',
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},
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{
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name: 'function argument is not an array but string',
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filename: 'app.e2e-spec.ts',
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code: 'test.each("string");',
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},
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{
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name: 'not in e2e test file',
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filename: 'non-e2e-test.ts',
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code: 'it.each([{}, {}, {}, {}, {}]);',
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},
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],
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invalid: [
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{
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name: 'when 6 objects are passed while 5 are allowed by default using "test.each"',
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filename: 'app.e2e-spec.ts',
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code: 'test.each([{}, {}, {}, {}, {}, {}])',
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output: null,
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errors: [
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{
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messageId: 'noLongArrays',
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data: {
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testFunctionName: 'test',
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actualLength: 6,
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limit: 5,
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},
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},
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],
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},
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{
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name: 'when 6 objects are passed while 5 are allowed by default using "it.each"',
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filename: 'app.e2e-spec.ts',
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code: 'it.each([{}, {}, {}, {}, {}, {}])',
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output: null,
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errors: [
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{
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messageId: 'noLongArrays',
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data: {
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testFunctionName: 'it',
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actualLength: 6,
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limit: 5,
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},
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},
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],
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},
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{
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name: 'when 2 objects are passed while 1 is allowed by passed option using "it.each"',
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filename: 'app.e2e-spec.ts',
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options: [{ limit: 1 }],
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code: 'it.each([{}, {}])',
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output: null,
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errors: [
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{
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messageId: 'noLongArrays',
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data: {
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testFunctionName: 'it',
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actualLength: 2,
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limit: 1,
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},
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},
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],
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},
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],
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});

‎src/custom-rules/no-long-arrays-in-test-each.ts

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import { AST_NODE_TYPES, ESLintUtils } from '@typescript-eslint/utils';
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type MessageIds = 'noLongArrays';
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type Options = [{ limit?: number }];
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const DEFAULT_LIMIT = 5;
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export const noLongArraysInTestEach = ESLintUtils.RuleCreator.withoutDocs<Options, MessageIds>({
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create(context, options) {
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return {
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CallExpression(node) {
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if (node.callee.type !== AST_NODE_TYPES.MemberExpression) {
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return;
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}
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if (
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node.callee.object.type !== AST_NODE_TYPES.Identifier ||
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!['test', 'it'].includes(node.callee.object.name)
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) {
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return;
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}
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if (node.callee.property.type !== AST_NODE_TYPES.Identifier || node.callee.property.name !== 'each') {
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return;
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}
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const firstArgument = node.arguments[0];
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if (firstArgument.type !== AST_NODE_TYPES.ArrayExpression) {
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return;
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}
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const limit = options[0].limit || DEFAULT_LIMIT;
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const elements = firstArgument.elements;
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if (elements.length <= limit) {
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return;
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}
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// eslint-disable-next-line @typescript-eslint/typedef
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const allElementsAreObjects = elements.every(element => element?.type === AST_NODE_TYPES.ObjectExpression);
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if (!allElementsAreObjects) {
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return;
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}
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context.report({
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node,
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messageId: 'noLongArrays',
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data: {
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testFunctionName: node.callee.object.name,
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actualLength: elements.length,
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limit: limit,
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},
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});
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},
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};
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},
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meta: {
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docs: {
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description:
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'Disallow using long arrays with objects inside `test.each()` or `it.each()`. Force moving them out of the file.',
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},
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messages: {
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// eslint-disable-next-line max-len
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noLongArrays:
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'Move the array with objects out of the test file in `{{ testFunctionName }}.each()`. Array length is {{ actualLength }}, but the limit is {{ limit }} items.',
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},
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type: 'suggestion',
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schema: [
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{
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type: 'object',
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properties: {
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limit: {
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type: 'integer',
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minimum: 1,
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},
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},
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additionalProperties: false,
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},
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],
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},
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defaultOptions: [{ limit: DEFAULT_LIMIT }],
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});

‎src/custom-rules/no-mixed-expectation-groups.ts

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},
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messages: {
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noMixedExpectationGroups:
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'Expectation for variable "{{ variable }}" should be moved above to the same place where it is check for the first time. Do not mix expectations of different variables.',
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'Expectation for variable "{{ variable }}" should be moved above to the same place where it is checked for the first time. Do not mix expectations of different variables.',
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},
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type: 'suggestion',
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schema: [],

‎src/plugin.spec.ts

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'no-useless-matcher-to-be-defined',
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'no-useless-matcher-to-be-null',
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'no-mixed-expectation-groups',
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'no-long-arrays-in-test-each',
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]);
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});
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‎src/plugin.ts

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'no-useless-matcher-to-be-defined': noUselessMatcherToBeDefined,
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'no-useless-matcher-to-be-null': noUselessMatcherToBeNull,
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'no-mixed-expectation-groups': noMixedExpectationGroups,
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'no-long-arrays-in-test-each': noMixedExpectationGroups,
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},
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} satisfies Linter.Plugin;

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