No coverage when running in watch mode

[MurakamiKennzo]

🐛 Bug Report

when I run jest --watch, I see unknown coverage.

To Reproduce

see Link repo.

Expected behavior

show correct coverage.

Link to repl or repo (highly encouraged)

jest-watch-coverage-bug

Run npx envinfo --preset jest

Paste the results here:

System:
    OS: macOS 10.14
    CPU: x64 Intel(R) Core(TM) m3-6Y30 CPU @ 0.90GHz
  Binaries:
    Node: 9.10.1 - /usr/local/bin/node
    npm: 6.4.1 - /usr/local/bin/npm
  npmPackages:
    jest: ^23.6.0 => 23.6.0 

[gabrielbs]

also happens on ubuntu 18.04

[villelahdenvuo]

Also hitting this issue even though there are changed tests that ran:

 PASS  src/app/product/reducers/product.reducer.spec.ts (6.041s)
 PASS  src/app/shared/services/resolve-store.service.spec.ts (6.706s)

=============================== Coverage summary ===============================
Statements   : Unknown% ( 0/0 )
Branches     : Unknown% ( 0/0 )
Functions    : Unknown% ( 0/0 )
Lines        : Unknown% ( 0/0 )
================================================================================

Test Suites: 2 passed, 2 total
Tests:       37 passed, 37 total
Snapshots:   0 total
Time:        10.329s
Ran all test suites related to changed files.

  System:
    OS: macOS 10.14.2
    CPU: (4) x64 Intel(R) Core(TM) i5-6360U CPU @ 2.00GHz
  Binaries:
    Node: 11.1.0 - ~/n/bin/node
    Yarn: 1.7.0 - ~/n/bin/yarn
    npm: 6.4.1 - ~/n/bin/npm
  npmPackages:
    jest: ^23.6.0 => 23.6.0

[SimenB]

@MurakamiKennzo what do you expect "correct coverage" to be? All 0? Unless tests actually execute, we have no way of knowing the coverage

[villelahdenvuo]

@SimenB I updated my comment above to be more clear. Tests are ran and coverage works when all tests are ran, but in watch more coverage is not collected even for the files that are affected.

[SimenB]

@villelahdenvuo that's a separate issue from the OP, please include a reproduction (maybe in a new issue)

[villelahdenvuo]

@SimenB How is it different from the OP? According to the example repo included in the OP the issue appears in watch mode after adding a new test. That is my case as well, at first I had no coverage as expected, but then I added a new tests to those two files shown and it still says coverage Unknown.

[SimenB]

Ah, sorry, I missed the step editing the test while watch mode was running.

@stipsan thoughts on how to fix this? You're my goto "coverage in watch mode" guy :D

[MurakamiKennzo]

I agree what @villelahdenvuo said. please follow the step and you will understand what i mean.

[stipsan]

I'll have to look into it more but on top of my head it sounds like the problem is related to the collectCoverageFrom patterns that are added in the runner: https://github.com/facebook/jest/blob/c01b4c75a2f65e9fa122adf69b0ac11875f1fc74/packages/jest-cli/src/runJest.js#L163-L188

So my theory is that it's generating a too exclusive pattern on the first run that is persisted through the second run with the added test.

[coxdn]

I have the same problem. When I delete a folder .git and reinit it (git init), then watch mode displays normally coverage. On repo from topic starter it works too.

In my case problem manifests on the project a bit larger and wouldn't want to hide this folder every time when I starting npm run test:watch. Maybe there are some workarounds?

[GuillaumeAmat]

Same issue here. When I launch Jest with jest --coverage --watch, without any modified files, the coverage is Unknown% ( 0/0 ).

If I press a, all the tests run, I can see each fail/success state, but the coverage remains Unknown% ( 0/0 ).

If I edit a file, the tests run and again, the coverage is Unknown% ( 0/0 ).

But! If I hit o, the tests run and I see the right coverage! I can then hit a or whatever and all is good :)

[kmarple1]

I'm getting the same bug, or a variant of it. When I first run npm run test, code coverage for changed files will be correct. However, if I press a or modify additional files, the appropriate tests will be run, but the files won't be added to the coverage report.

[miikaah]

It seems like jest doesn't really respect collectCoverageFrom in watch mode and instead overrides it with files that have changed. If there are no changes, no code coverage is gathered, even if new tests have stepped over new lines. It's a major drag when one has to write tests to a codebase afterwards.

As a workaround I found that you can use forceCoverageMatch to gather coverage even in watch mode.