[pve-eslint.git] / eslint / docs / developer-guide / unit-tests.md

# Unit Tests

Most parts of ESLint have unit tests associated with them. Unit tests are written using [Mocha](https://mochajs.org/) and are required when making contributions to ESLint. You'll find all of the unit tests in the `tests` directory.

When you first get the source code, you need to run `npm install` once initially to set ESLint for development. Once you've done that, you can run the tests via:

    npm test

This automatically starts Mocha and runs all tests in the `tests` directory. You need only add yours and it will automatically be picked up when running tests.

## Running Individual Tests

If you want to quickly run just one test file, you can do so by running Mocha directly and passing in the filename. For example:

    npm run test:cli tests/lib/rules/no-wrap-func.js

If you want to run just one or a subset of `RuleTester` test cases, add `only: true` to each test case or wrap the test case in `RuleTester.only(...)` to add it automatically:

```js
ruleTester.run("my-rule", myRule, {
    valid: [
        RuleTester.only("const valid = 42;"),
        // Other valid cases
    ],
    invalid: [
        {
            code: "const invalid = 42;",
            only: true,
        },
        // Other invalid cases
    ]
})
```

Running individual tests is useful when you're working on a specific bug and iterating on the solution. You should be sure to run `npm test` before submitting a pull request. `npm test` uses Mocha's `--forbid-only` option to prevent `only` tests from passing full test runs.

## More Control on Unit Testing

`npm run test:cli` is an alias of the Mocha cli in `./node_modules/.bin/mocha`. [Options](https://mochajs.org/#command-line-usage) are available to be provided to help to better control the test to run.
Commit	Line	Data
eb39fafa DC	1	# Unit Tests
	2
	3	Most parts of ESLint have unit tests associated with them. Unit tests are written using [Mocha](https://mochajs.org/) and are required when making contributions to ESLint. You'll find all of the unit tests in the `tests` directory.
	4
	5	When you first get the source code, you need to run `npm install` once initially to set ESLint for development. Once you've done that, you can run the tests via:
	6
	7	npm test
	8
	9	This automatically starts Mocha and runs all tests in the `tests` directory. You need only add yours and it will automatically be picked up when running tests.
	10
	11	## Running Individual Tests
	12
609c276f	13	If you want to quickly run just one test file, you can do so by running Mocha directly and passing in the filename. For example:
eb39fafa DC	14
	15	npm run test:cli tests/lib/rules/no-wrap-func.js
	16
609c276f TL	17	If you want to run just one or a subset of `RuleTester` test cases, add `only: true` to each test case or wrap the test case in `RuleTester.only(...)` to add it automatically:
	18
	19	```js
	20	ruleTester.run("my-rule", myRule, {
	21	valid: [
	22	RuleTester.only("const valid = 42;"),
	23	// Other valid cases
	24	],
	25	invalid: [
	26	{
	27	code: "const invalid = 42;",
	28	only: true,
	29	},
	30	// Other invalid cases
	31	]
	32	})
	33	```
	34
	35	Running individual tests is useful when you're working on a specific bug and iterating on the solution. You should be sure to run `npm test` before submitting a pull request. `npm test` uses Mocha's `--forbid-only` option to prevent `only` tests from passing full test runs.
eb39fafa DC	36
	37	## More Control on Unit Testing
	38
	39	`npm run test:cli` is an alias of the Mocha cli in `./node_modules/.bin/mocha`. [Options](https://mochajs.org/#command-line-usage) are available to be provided to help to better control the test to run.