22

If I run

npm test --coverage

the tests pass, but the coverage is not run.

When I change package.json to have

react-scripts test --coverage

Then, when I do npm test and a it runs the tests but not the coverage

The tests run along with the coverage report but the coverage shows all zeroes for coverage

 PASS  src/components/Header/SubHeader.test.js
  The <SubHeader /> component
    ✓ should render (4ms)
    ✓ should render with a goback button (1ms)
    ✓ should render

----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |        0 |        0 |        0 |        0 |                   |
----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       3 passed, 3 total
Snapshots:   3 passed, 3 total
Time:        1.077s
Ran all test suites.

Finally, I realized that I can do

npm run test .

Question: Why don't the other methods work?

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5
  • 7
    Which version of CRA and Jest are you using? I've had an issue in the past and using npm run test -- --coverage --watchAll=false did the trick for me (not optimal but...) Commented Sep 2, 2020 at 9:39
  • Note your first problem is explicitly called out in the docs - you're missing --, so --coverage goes to npm run not react-scripts test. That's not related to CRA/Jest, it's just how NPM scripts work. The second seems to be a bug: github.com/facebook/create-react-app/issues/7838. Commented Sep 2, 2020 at 10:00
  • Hey Michael, i edite my answer and figured out what was the deal. Please take a look. I guess there is more to explain why --coverage is not passed with npm, but . is passed Commented Sep 7, 2021 at 11:58
  • Hey Michael, finally i got the answer to your question. I asked SO community myselft about . being passed and it regards the option and positional parameter. Take a look at my answer, i edited it Commented Sep 14, 2021 at 13:56
  • I'm sure this solution will work for you: stackoverflow.com/a/76001983/5650332 Commented Apr 13, 2023 at 5:52

2 Answers 2

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25

After revisiting this question i figured out that if you run this you will trigger coverage command and get all results.

SOLUTION 1

npm run test -- --coverage .

When you are passing arguments to npm script, you need to add -- before adding arguments like --coverage. This is just how npm works. See this answer for passing arguments to npm

SOLUTION 2

yarn test --coverage .

EDIT:

I asked a question regarding . being passed down the command and answer is pretty much simple. . is passed because it is a positional parameter, in contrast to --coverage that is option for npm test command: Why is . passed as argument to npm without -- delimiter?

---- Problem analysis ----

PROBLEM 1

npm test --coverage you are not passing --coverage argument to test script.

In the other case when you edit script to be:

react-scripts test --coverage and run npm test here you actually add argument --coverage, but in script itself, not from npm command

PROBLEM 2

When you do npm run test . you are passing . that means you want to include all files in this command.

For some reason . is passed to the npm run test script but not --coverage.

On the other side yarn passes all arguments without --.

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npm run test -- --coverage --watchAll=false
2

I do it this way:

npm run test -- --coverage --watchAll

the --watchAll makes it run code coverage for the entire project, instead of just the files that have been changed.

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