How to get the code coverage report using Jest?

Question

Is there a way to have code coverage in the JavaScript Jest testing framework, which is built on top of Jasmine?

The internal framework does not print out the code coverage it gets. I've also tried using Istanbul, blanket, and JSCover, but none of them work.

I'm not very into jest, but have you seen [config.collectCoverage](http://facebook.github.io/jest/docs/api.html#config-collectcoverage-boolean)? — Ciro Costa, Aug 24 '14 at 15:47

score 337 · Accepted Answer · edited Oct 19 '18 at 19:23

337

When using Jest 21.2.1, I can see code coverage at the command line and create a coverage directory by passing --coverage to the Jest script. Below are some examples:

I tend to install Jest locally, in which case the command might look like this:

npx jest --coverage

I assume (though haven't confirmed), that this would also work if I installed Jest globally:

jest --coverage

The very sparse docs are here

When I navigated into the coverage/lcov-report directory I found an index.html file that could be loaded into a browser. It included the information printed at the command line, plus additional information and some graphical output.

edited Oct 19 '18 at 19:23

Alex Lomia

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answered Oct 24 '17 at 19:39

ccalvert

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Never use global modules. To ensure version consistency, and package presence, always use the executable in `node_modules` via `./node_modules/.bin/jest --coverage`. As long as the package is named in package.json, you can guarantee execution with the exact version of jest you expect. – taystack Jan 28 '19 at 14:48
How to get jest coverage only for changed files? – Shanika Ediriweera Nov 27 '19 at 05:59
1

Is there an easy way to fail tests if coverage is below a certain limit? Corresponding SO-question: https://stackoverflow.com/questions/60512167/how-to-check-jest-coverage-in-console – Stefan Mar 03 '20 at 17:03
@ShanikaEdiriweera https://jestjs.io/docs/en/cli.html#--collectcoveragefromglob – marcellothearcane May 07 '20 at 07:45
Can we change location of 'coverage' directory? – aagjalpankaj Jan 24 '22 at 23:13
Is there a way to calculate coverage without running tests? Kinda like a dry run? – Ali Mert Çakar Jan 09 '23 at 18:31
@aagjalpankaj Yes, by specifying a `collectCoverageFrom` array as documented [here](https://jestjs.io/docs/configuration#collectcoveragefrom-array). – Mike Lowery Jun 30 '23 at 21:18

score 117 · Answer 2 · edited Jul 20 '18 at 09:23

117

UPDATE: 7/20/2018 - Added links and updated name for coverageReporters.

UPDATE: 8/14/2017 - This answer is totally outdated. Just look at the Jest docs now. They have official support and documentation about how to do this.

@hankhsiao has got a forked repo where Istanbul is working with Jest. Add this to your dev dependencies

 "devDependencies": {
     "jest-cli": "git://github.com/hankhsiao/jest.git"
 }

Also make sure coverage is enabled in your package.json jest entry and you can also specify formats you want. (The html is pretty bad ass).

 "jest": {
     "collectCoverage": true,
     "coverageReporters": ["json", "html"],
 }

See Jest documentation for coverageReporters (default is ["json", "lcov", "text"])

Or add --coverage when you invoke jest.

edited Jul 20 '18 at 09:23

bformet

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answered Dec 15 '14 at 08:22

Adrian Adkison

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The coverageFormats option has been removed -- looks like json and html are both generated every time. – Mar 01 '15 at 15:47
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I use the --coverage option but absolutely nothing different happens. – gbbr Mar 02 '15 at 13:28
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It's (now) called `coverageReporters` and the default is `["json", "lcov", "text"]`. See http://facebook.github.io/jest/docs/configuration.html#coveragereporters-array-string – Karsten S. Apr 13 '17 at 18:32
dont work, Unknown option "coverageFormats" with value ["json", "html"] was found. – srghma Aug 12 '17 at 18:32
1

Thanks, setting coverageReporters: ["json", "lcov", "text"] in jest.config.ts fixed the issue for me. – Sachintha Udara Mar 20 '23 at 17:45

score 100 · Answer 3 · edited Feb 09 '21 at 00:30

100

Jan 2019: Jest version 23.6

For anyone looking into this question recently especially if testing using npm or yarn directly

Currently, you don't have to change the configuration options

As per Jest official website, you can do the following to generate coverage reports:

1- For npm:

You must put -- before passing the --coverage argument of Jest

npm test -- --coverage

if you try invoking the --coverage directly without the -- it won't work

2- For yarn:

You can pass the --coverage argument of jest directly

yarn test --coverage

edited Feb 09 '21 at 00:30

Peter Mortensen

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answered Jan 13 '19 at 21:55

Ahmed Elkoussy

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How to get jest coverage only for changed files? – Shanika Ediriweera Nov 27 '19 at 06:00
Changed since when? You probably want to use the `--watch` setting for this. – koehn Mar 17 '20 at 16:04
6

This answer makes a lot of assumptions about the state of ones `package.json`. – airtonix Jun 06 '20 at 00:06
This gives me coverage for files under /test folder. Definitely not what I was looking for :D – Davor Jan 13 '21 at 17:09
I am late here, can I know if we can get the time to take coverage for each test case as well as the test suite to the outputFile? – Mithun Shreevatsa Feb 22 '22 at 07:11

score 22 · Answer 4 · edited Feb 09 '21 at 00:32

22

This works for me:

 "jest": {
    "collectCoverage": true,
    "coverageReporters": ["json", "html"]
  },
  "scripts": {
    "test": "jest  --coverage"
  },

Run:

yarn/npm test

edited Feb 09 '21 at 00:32

Peter Mortensen

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answered Nov 07 '20 at 16:56

Deen John

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what is this file? Where does this JSON text go? – Stealth Rabbi Nov 17 '21 at 13:45
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Should be `package.json`. – Saikat Dec 05 '21 at 07:26
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These config properties can also be included in `jest.config.js` if you have a lot of configs that you don't want cluttering up the `package.json` file. See Jest docs: https://jestjs.io/docs/configuration – dmbaughman Jun 21 '22 at 17:29

score 11 · Answer 5 · answered May 18 '21 at 18:22

11

You can run npx jest --coverage -- path/to/your/file.spec.js that will show coverage for affected files

If you want to view this in browser you can do as follows,

Go to Browser and CMD+O.
Navigate to your repo and search for coverage/lcov-report/index.html

Then you can visually see all the coverage areas.

You can also refer to this link below, for more information https://dev.to/stevescruz/awesome-jest-tip-coverage-report-h5j

answered May 18 '21 at 18:22

Anusha Bhat

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any idea why is this showing me "unknown %"? – Dani Mar 23 '23 at 11:15

score 7 · Answer 6 · edited Feb 09 '21 at 00:10

7

Check the latest Jest (v 0.22): https://github.com/facebook/jest
The Facebook team adds the Istanbul code coverage output as part of the coverage report and you can use it directly.
After executing Jest, you can get a coverage report in the console and under the root folder set by Jest, you will find the coverage report in JSON and HTML format.
FYI, if you install from npm, you might not get the latest version; so try the GitHub first and make sure the coverage is what you need.

edited Feb 09 '21 at 00:10

Peter Mortensen

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answered Nov 06 '14 at 01:08

Winters Huang

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The question was how to get Code coverage for Jest. That Istanbul and Jest don't work together might be true, but that doesn't answer the question. – David Raab Nov 06 '14 at 01:52

score 4 · Answer 7 · answered Jun 10 '19 at 14:43

If you are having trouble with --coverage not working it may also be due to having coverageReporters enabled without 'text' or 'text-summary' being added. From the docs: "Note: Setting this option overwrites the default values. Add "text" or "text-summary" to see a coverage summary in the console output." Source

score 2 · Answer 8 · answered Sep 30 '19 at 04:38

2

Configure your package.json file

"test": "jest --coverage",

Now run:

yarn test

All the test will start running and you will get the report.

answered Sep 30 '19 at 04:38

Saif Siddiqui

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score -12 · Answer 9 · edited Feb 09 '21 at 00:13

-12

I had the same issue and I fixed it as below.

install yarn npm install --save-dev yarn
install jest-cli npm install --save-dev jest-cli
add this to the package.json "jest-coverage": "yarn run jest -- --coverage"

After you write the tests, run the command npm run jest-coverage. This will create a coverage folder in the root directory. /coverage/icov-report/index.html has the HTML view of the code coverage.

edited Feb 09 '21 at 00:13

Peter Mortensen

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answered Feb 08 '17 at 23:56

Laksh

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There is no need to install yarn. Yarn is just different package manager to NPM – Black Jul 14 '17 at 06:51
initial `--` it is just needed using npm, yarn pass all arguments to jest. – Angel Fraga Parodi Jan 20 '21 at 12:18
this answer is misleading – JayantSeth Jun 22 '23 at 07:16

How to get the code coverage report using Jest?

9 Answers9

Jan 2019: Jest version 23.6

1- For npm:

2- For yarn:

Linked