How do I test a single file using Jest

Question

I am able to test multiple files using Jest  but I cannot figure out how to test a single file  I have   Run npm install jest-cli --save-dev Updated package json          quot scripts quot      quot test quot    quot jest quot          Written a number of tests   Running npm test works as expected  currently it runs 14 tests   How do I test a single file  e g  test app foo   tests   bar spec js  I have tried running npm test app foo   tests   bar spec js  from the project root   but I get the following error   npm ERR  Error  ENOENT  open   node modules app foo tests bar spec js package json

User · Answer

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

User · Answer

At this time  I did it by using  yarn test TestFileName spec js  You shouldn t put the complete path  That works for me on a Windows 10 machine

User · Answer

From Jest documentation    quot scripts quot          quot test quot    quot jest path to my-test js quot       Run this with  npm run 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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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  amp  more information  How to test a single Jest test file in Nx  6

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For nestjs users  the simple alternative is to use  npm test -t  lt name of the spec file to run gt   Nestjs comes preconfigured with the regex of the test files to search for incase 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 confuguration which is available by default incase of nestjs  quot jest quot          quot moduleFileExtensions quot            quot js quot          quot json quot          quot ts quot              quot rootDir quot    quot src quot        quot testRegex quot    quot  spec ts  quot        quot transform quot            quot        t j s  quot    quot ts-jest quot              quot coverageDirectory quot    quot    coverage quot        quot testEnvironment quot    quot node quot

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Since at least 2019  npm test -- SomeTestFileToRun 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

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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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If you install VSCode plugin Jest Runner  You will have Debug Run options above every describe and it   You can open your test file in VSCode and click on one of those options

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import LoggerService from     LoggerService     describe  Method called            gt      it  00000000        gt        const logEvent   jest spyOn LoggerService   logEvent        expect logEvent  toBeDefined               Usage  npm test --   tests   LoggerService test ts -t  00000000

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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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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 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            quot scripts quot          quot test quot    quot jest quot        quot testw quot    quot jest --watch quot        quot testc quot    quot jest --coverage quot               quot devDependencies quot          quot jest quot    quot  18 1 0 quot

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

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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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Using npm test doesn t mean Jest is installed globally  It just means  quot test quot  is mapped to using Jest in your package json file  The following is what worked for me  at the root level of the project  node modules  bin jest  args   args 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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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   For Windows   to be updated

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We are using nrwl-nx with Angular  In this case we can use this command  npm test  lt ng-project gt  -- --testFile  quot file-name-part quot   Notes   npm test will run the test script specified in package json   quot test quot    quot ng test quot  Thus the rest of the cmd will be passed to ng test   lt ng-project gt  is the name of a project in angular json  when you omit this parameter  the  quot defaultProject quot   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  quot project quot  -  quot  lt ng-project gt  quot  -  quot architect quot  -  quot test quot  and check the  quot builder quot   which in our case is   quot  nrwl jest jest quot    Now that we know the builder  we need to find the available cmd-line parameters  On the command line  run npm test  lt ng-project gt  -- --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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If you are running npm  gt   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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All you have to do is chant the magick incantation  npm test -- SomeTestFileToRun  The standalone -- 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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quot test quot    quot jest api ds server ds server test js quot

[node.js] How do I test a single file using Jest?

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