Functional components lose displayName when running coverage

Description

Coverage fails to run tests correctly, resulting in failed tests that are actually passing when run without --coverage.

Expected behavior

Passing tests should still pass when i add --coverage

Actual behavior

Tests that are passing without --coverage are failing when i add --coverage.

Environment

Run these commands in the project folder and fill in their results:

1. npm ls react-scripts (if you haven’t ejected): UNMET PEER DEPENDENCY eslint-plugin-import@2.0.1
2. node -v: v6.9.1
3. npm -v: 3.10.9

Then, specify:

1. Operating system: OSX Sierra 10.12
2. Browser and version: Safari 10.0

[wyze]

This is fixed as of babel-plugin-istanbul@3.1.2. I just did a fresh project with create-react-app and was able to use npm test -- --coverage successfully.

Note that displayName is only set when you define your component and use that variable as the default export. If you follow the 2nd example, the displayName isn’t set and defaults to Component, but this still passes when checking coverage.

// Works
const Hello = () => <div>Hello</div>

export default Hello

// Doesn't work
export default () => <div>Hello</div>

[gaearon]

Awesome, thanks for reporting back. Closing this.

I sent a PR to Jest to enforce a minimal version in the future, but for now existing users can get the fix by removing node_modules and running npm install again.