How do I test a single file using Jest?

Since at least 2019:

npm test -- bar.spec.js

In 2015:

In order to run a specific test, you'll need to use the jest command. npm test will not work. To access jest directly on the command line, install it via npm i -g jest-cli or yarn global add jest-cli.

Then simply run your specific test with jest bar.spec.js.

Note: You don't have to enter the full path to your test file. The argument is interpreted as a regular expression. Any part of the full path that uniquely identifies a file suffices.

---

All you have to do is chant the magic incantation:

npm test -- SomeTestFileToRun

The stand-alone -- is *nix magic for marking the end of options, meaning (for NPM) that everything after that is passed to the command being run, in this case jest. As an aside, you can display Jest usage notes by saying

npm test -- --help

Anyhow, chanting

npm test -- Foo

runs the tests in the named file (FooBar.js). You should note, though, that:

Jest treats the name as case-sensitive, so if you're using a case-insensitive, but case-preserving file system (like Windows NTFS), you might encounter what appears to be oddness going on.

Jest appears to treat the specification as a prefix.

So the above incantation will

Run FooBar.js, Foo.js and FooZilla.js

But not run foo.js

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To run an individual test:

npm test -t ValidationUtil # `ValidationUtil` is my module `ValidationUtil.spec.js`

-t - after it, put a regular expression containing the test name.

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If you install the Visual Studio Code plugin Jest Runner,

https://i.stack.imgur.com/OMXNT.png

You will have Debug/Run options above every describe and it.

https://i.stack.imgur.com/xDtz0.png

You can open your test file in Visual Studio Code and click on one of those options.

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If you use Yarn, you can add the .spec.js or .test.js file directly after:

yarn test src/lib/myfile.test.js

This is the part from my package.json file with Jest installed as a local package (removed the relevant parts):

{
...
  "scripts": {
    "test": "jest",
    "testw": "jest --watch",
    "testc": "jest --coverage",
...
  },
  "devDependencies": {
    "jest": "^18.1.0",
    ...
  },

}

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Using npm test doesn't mean Jest is installed globally. It just means "test" is mapped to using Jest in your package.json file.

The following works, at the root level of the project:

npx jest [file or directory]

file or directory can be the test file you want to run or the directory containing multiple files.

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You could use the file name with npm test --:

npm test -- fileName.jsx 

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We are using nrwl-nx with Angular. In this case we can use this command:

npm test <ng-project> -- --testFile "file-name-part"

Notes:

npm test will run the test script specified in package.json: "test": "ng test"

--: tells npm to pass the following parameters to the test script (instead of consuming them)

Thus the rest of the cmd will be passed to ng test is the name of a project in angular.json when you omit this parameter, the "defaultProject" (specified in angular.json) will be used (so you must specify it, when the test is not in your default project) Next we must check which builder is used: In angular.json navigate to "project" - "" - "architect" - "test" and check the "builder", which in our case is: "@nrwl/jest:jest" Now that we know the builder, we need to find the available cmd-line parameters On the command line, run npm test -- --help to see all available options Or check the online documentation One of the options is --testFile which is used here

is the name of a project in angular.json when you omit this parameter, the "defaultProject" (specified in angular.json) will be used (so you must specify it, when the test is not in your default project)

when you omit this parameter, the "defaultProject" (specified in angular.json) will be used (so you must specify it, when the test is not in your default project)

Next we must check which builder is used: In angular.json navigate to "project" - "" - "architect" - "test" and check the "builder", which in our case is: "@nrwl/jest:jest"

In angular.json navigate to "project" - "" - "architect" - "test"

and check the "builder", which in our case is: "@nrwl/jest:jest"

Now that we know the builder, we need to find the available cmd-line parameters On the command line, run npm test -- --help to see all available options Or check the online documentation

On the command line, run npm test -- --help to see all available options

Or check the online documentation

One of the options is --testFile which is used here

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To run a specific test in a specific file:

yarn test -f "partial-filename" -t "as split node"

npm test, or jest can replace yarn test, depending on your preferred JS bundler.

This would only attempt to find tests in files that contained some-partial-filename, and within those files, the test would need to have a describe or it directive that mentions "as split node", for example

// In cool-partial-filename.js
describe("with a less indented sibling", () => {
  it("should create a new check-list-item with the same indent as split node", () => {
    console.log("This would run with the invocation above");
  })
})

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If you are running npm >= 5.2.0 and you have installed Jest locally as a devDependencies with npm i -d jest, you can run Jest on a particular file by doing npx jest /path/to/your/spec.js.

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It can also be achieved by:

jest --findRelatedTests path/to/fileA.js

Reference (Jest CLI Options)

How can that be achieved in the Nx monorepo? Here is the answer (in directory /path/to/workspace):

npx nx test api --findRelatedTests=apps/api/src/app/mytest.spec.ts

Reference & more information: How to test a single Jest test file in Nx #6

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At that time, I did it by using:

yarn test TestFileName.spec.js

You shouldn't put in the complete path. That works for me on a Windows 10 machine.

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If you dont want to install jest globally you can use

npx jest foo.test.js

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With a package.json script

With "scripts": { "test": "jest" } in package.json:

npm test -- foo/__tests__/bar.spec.js

Using jest-cli directly

Globally-installed:

jest foo/__tests__/bar.spec.js

Locally-installed:

./node_modules/.bin/jest foo/__tests__/bar.spec.js

Using --testPathPattern

The --testPathPattern option has the equivalent effect of passing paths as unnamed positional arguments to jest-cli. See normalize.ts.

./node_modules/.bin/jest --testPathPattern foo/__tests__/bar.spec.js

Testing two or more specific files

Separate filenames with commas or spaces:

./node_modules/.bin/jest foo/__tests__/bar.spec.js,foo/__tests__/foo.spec.js

./node_modules/.bin/jest foo/__tests__/bar.spec.js foo/__tests__/foo.spec.js

Pass --testPathPattern multiple times:

./node_modules/.bin/jest --testPathPattern foo/__tests__/bar.spec.js --testPathPattern foo/__tests__/foo.spec.js

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This is how I dynamically run tests on a specific file without restarting the test.

My React project was created as create-react-app.

So it watches test for changes, automatically running test when I make changes.

So this is what I see at the end of the test results in the terminal:

Test Suites: 16 passed, 16 total
Tests:       98 passed, 98 total
Snapshots:   0 total
Time:        5.048s
Ran all test suites.

Watch Usage: Press w to show more.

Press W

Watch Usage
 › Press f to run only failed tests.
 › Press o to only run tests related to changed files.
 › Press q to quit watch mode.
 › Press p to filter by a filename regex pattern.
 › Press t to filter by a test name regex pattern.
 › Press Enter to trigger a test run.

Then press P

Pattern Mode Usage
 › Press Esc to exit pattern mode.
 › Press Enter to filter by a filenames regex pattern.

 pattern ›

 Start typing to filter by a filename regex pattern.

This is after I wanted to run the 'index.es6.js' file in the 'Login' folder:

Pattern Mode Usage
 › Press Esc to exit pattern mode.
 › Press Enter to filter by a filenames regex pattern.

 pattern › login/index

 Pattern matches 1 file
 › src/containers/Login/index.es6.test.js

That's how I run tests on a specific file.

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A simple solution that works:

yarn test -g fileName or

npm test -g fileName

Example:

yarn test -g cancelTransaction or

npm test -g cancelTransaction

More about test filters:

Test Filters
--fgrep, -f Only run tests containing this string [string]
--grep, -g Only run tests matching this string or regexp [string]
--invert, -i Inverts --grep and --fgrep matches [boolean]

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The simple way is to run a single unit test file, is inside the root folder run the command in the terminal.

npm test <fileName.test.js>

// For example
npm test utils.test.js

I have also tried the Jest Runner Extensions for Visual Studio Code, and it works great.

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Use this command:

npx jest test --runTestsByPath <path-to-file>

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The below command worked for me.
npx jest -i file-name

No need to specify complete path of the file, filename is sufficient.

Edit : Found another way to do it.
npm run test:functional -i file-name for Functional Test
npm run test:integration -i file-name for Integration Test

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There isn't any need to pass the full path. Just use a regular expression pattern.

See --testLocationInResults.

yarn jest --testNamePattern my_test_name
yarn jest -t=auth
yarn jest -t component # This will test all whose test name contains `component`

yarn jest --testPathPattern filename # This will match the file path
yarn jest filename # This will match the file path, the same with above

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Jest and Jest Runner are super useful VSCode extensions when you working on jest.

Jest An automatic test runner

Jest Runner Adds "Run | Debug" code lens above the test to run or debug a single test.

https://i.stack.imgur.com/S2fmJ.png

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I just installed Jest as global, ran jest myFileToTest.spec.js, and it worked.

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Do this if you are using yarn

yarn test nameofthefile

eg:

yarn test file.test.js

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You have two options:

Option 1: Command line. You can run the following command node '/Users/complete-path-to-you-project/your-project/node_modules/.bin/jest' '/Users/complete-path-to-you-project/your-project/path-to-your-file-within-the-project/your-file.spec.ts' This avoids you to install Jest globally. You use the jest used by your project.

Option 2: If you are using Visual Studio Code you have a great plugin to do this: Jest Runner. It allows you not only to run tests file by file, but even specific suites and specs just by a right click on the tests you want to run.

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With Angular and Jest you can add this to file package.json under "scripts":

"test:debug": "node --inspect-brk ./node_modules/jest/bin/jest.js --runInBand"

Then to run a unit test for a specific file you can write this command in your terminal

npm run test:debug modules/myModule/someTest.spec.ts

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From the Jest documentation:

  "scripts": {
    "test": "jest path/to/my-test.js"
  }

Run this with

 npm run test

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Just use this command to run and check the coverage of the particular file.

yarn run test Index.js -u --coverage --watchAll=false

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Jest will use what you pass as a regular expression pattern. That it will match for.

If you want to run a specific test file, then the best way to do it is to use the precise full path to it. (You can too specify a certain relative path like (src/XFolder/index.spec.ts)).

The easiest way to provide the full path being in the directory and in Linux is:

jest $PWD/index.spec.ts

Note the use of the variable $PWD.

https://i.stack.imgur.com/fHKVh.png

For Windows! (to be updated)

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import LoggerService from '../LoggerService ';

describe('Method called****', () => {
  it('00000000', () => {
    const logEvent = jest.spyOn(LoggerService, 'logEvent');
    expect(logEvent).toBeDefined();
  });
});

Usage:

npm test -- __tests__/LoggerService.test.ts -t '00000000'

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For NestJS users, the simple alternative is to use,

npm test -t <name of the spec file to run>

NestJS comes preconfigured with the regex of the test files to search for in case of Jest.

A simple example is -

npm test -t app-util.spec.ts

(that is my .spec file name)

The complete path need not be given since Jest searches for .spec files based on the configuration which is available by default in case of NestJS:

"jest": {
    "moduleFileExtensions": [
      "js",
      "json",
      "ts"
    ],
    "rootDir": "src",
    "testRegex": ".spec.ts$",
    "transform": {
      "^.+\\.(t|j)s$": "ts-jest"
    },
    "coverageDirectory": "../coverage",
    "testEnvironment": "node"
  }
}

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