33

We need to check test coverage for our React.js app and ideally get lcov.info output to send to a third-party coverage tracker like Coveralls or CodeClimate

Its unclear from the Jest API how to get test coverage information when running tests.

There's an Open Issue on GitHub: https://github.com/facebook/jest/issues/101 and associated Pull Request: https://github.com/facebook/jest/pull/178 but the PR still has not been merged by the Jest core team.

Is there an alternative way of getting coverage info that works today?

Note: I'm aware of @adrian-adkison suggestion in: https://stackoverflow.com/a/27479903/1148249 but @hankhsiao's fork is quite out-of-date with jest-cli since he submitted the Pull Request 2.5 months ago...

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6 Answers 6

Reset to default
44 
npm test -- --coverage

note that extra -- in the middle, docs

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4 Comments

what does that extra -- do?
whatever follows -- are arguments that npm will pass to the script being run, in this case probably jest. Will result in jest --coverage
This should be the accepted answer.
I have a react app created from create-react-app, to get the coverage I ran npm test -- --coverage and it worked for me, Thanks.
19

@hankhsiao's fork has been merged. I have been using the latest https://github.com/facebook/jest and getting great results. 

jest --coverage
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1 Comment

This failed for TypeScript React project.
4

In your package.json under the script section add this piece of code -

test: react-scripts test --coverage
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1

You can either run jest through

jest --coverage

or you can also set "collectCoverage" to true in your jest configuration inside your package.json. This way the coverage report will be generated everytime you run jest.

Although you should know that this can increase the time taken for your tests to run significantly.

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1

In my package.json

 "scripts": {
    ...
    "test": "react-scripts test",
    "test:coverage": "react-scripts test --coverage",
    ...
  },

to see test coverage

yarn test:coverage
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1

package.json

"scripts": {
    ...
    "test": "react-scripts test",
    ...
  },

run command

npm run test -- --watchAll=false  --coverage

you can also check in details

 /coverage/icov-report/src/...<file>.html
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