Out of the box test coverage is not 100%

[TheRobBrennan]

I love this as a starting point for React apps, but I am puzzled by one thing...Having Jest and test coverage built in is awesome, but why isn't coverage 100% out of the box?

If I run the test coverage report, I see:

[Thu Jan 12 11:29:25] fb $ npm test -- --coverage

> fb@0.1.0 test /Users/rob/repos/fb
> react-scripts test --env=jsdom "--coverage"

 PASS  src/App.test.js
  ✓ renders without crashing (18ms)

----------|----------|----------|----------|----------|----------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |
----------|----------|----------|----------|----------|----------------|
All files |       50 |      100 |      100 |       50 |                |
 App.js   |      100 |      100 |      100 |      100 |                |
 index.js |        0 |      100 |      100 |        0 |              1 |
----------|----------|----------|----------|----------|----------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.137s
Ran all test suites.

It'd be great to start folks off with 100% tested code - no matter how trivial the index.js file is =)

[wtgtybhertgeghgtwtg]

Does index.js even have any exports?

[TheRobBrennan]

It doesn't - but it seems like if code coverage is something that is a huge benefit, it'd be great to start folks off with 100% coverage. For the life of me, all the googling I did regarding Jest and configuration options didn't seem to matter one bit for this.

[gaearon]

Thanks for the issue! I understand where you're coming from, but in real apps the goal of 100% test coverage is often unrealistic and encourages people to create brittle tests that aren't very useful.

I think it’s fine to leave this as is, but I appreciate your opinion.

[wasifhyder]

@TheRobBrennan -

You can exclude index.js from coverage reporting.

I remedied the problem by adding
Note: this worked for me on the ejected version of create-react-app. Can't say for sure how this would behave otherwise

"jest": { "coveragePathIgnorePatterns": ["<rootDir>/src/index.js"] }

https://facebook.github.io/jest/docs/configuration.html#coveragepathignorepatterns-array-string

[sebastienbarre]

@wasifhyder thanks, this looks promising. This isn't working for me though. I added what you mentioned above in package.json, and I'm running react-scripts test --env=jsdom --coverage, yet index.js is still brought up (with 0 coverage). Did you run it differently?

[thecristen]

I'm experiencing the same issue. I can't tell if these Jest configs work on an unejected app at all.

edit: However I did have luck adjusting the CLI script. Adding this flag worked for me --collectCoverageFrom='["src/**/*.{js,jsx}", "!src/index.js"]'

[wasifhyder]

@sebastienbarre, @thecristen

I did this after ejecting react. Haven't tried without ejecting, so can't say for sure how this will behave.

[gaearon]

Coverage collection is configurable in the next version.
#1830

[gaearon]

Please help beta test the new version that includes this change!
#2172