Support Jest coverageThreshold option

[lacroixthomas]

I would like to configure the coverage threshold from jest to be able to launch jenkins from CI with a 90-100% coverage.
Can we have support for this in Create react app ?

What is the most relevant:

• Overriding some part of the config ? https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/scripts/test.js#L34 I can do a PR fo it
• Keep it like this and I have to override the whole configuration with --config="{}" from package.json ?

[gaelollivier]

Any insights on this ? Could be nice to provide custom config to Jest :)

[mpj]

I would really like to be able to use the jest config options in package.json. Some of the defaults (such as bail=false) are very, very annoying. I don't think this would create much entropy.

[gaearon]

Some of the defaults (such as bail=false) are very, very annoying.

File an issue and describe your use case? It’s really hard to guess that something is “very annoying” if nobody tells us about it. 😉 A lot of those might not be conscious decisions so you should question them in issues by explaining your use cases.

[gaelollivier]

@gaearon What about the coverageTreshold then ? I don't think it can be a default, that's something that must be decided for each project

[gaearon]

@gaelduplessix We intend to add some configurability in the future. I'm not closing the issue but now is not the time yet. Perhaps in a few months when more things shake out (e.g. Jest has been going through a ton of changes recently).

[devilleweppenaar]

Jest configurability would be excellent, thanks!

For now, this is how we achieve coverage threshold checking on CI:

"coverage": "CI=true npm t -- --coverage",
"postcoverage": "istanbul check-coverage --statements 90 --functions 90 --branches 90 --lines 90",

[jagregory]

Chiming in here (or should I raise a new issue?), but I'd like to be able to set the shapshotSerializers option for Jest so I can use enzyme and snapshot testing together transparently. See: https://www.npmjs.com/package/jest-serializer-enzyme

This would be trivial, if create-react-app allowed Jest configuration in package.json.

Naively, I'm wondering if utils/createJestConfig.js could be updated to merge package.json config if it exists. Something like:

const config = {
  collectCoverageFrom: ['src/**/*.{js,jsx}'],
  /* ... */
};

if (rootDir) {
  config.rootDir = rootDir;
}

return {
   ...config,
   ...packageJson.jest,
};

[gaearon]

@jagregory You should be able to use expect.addSnapshotSerializer() in src/setupTests.js instead. Let me know if that works.

[jagregory]

@gaearon Do you know which Jest version that function is available? I'm using CRA 0.9.5, which has Jest 18.1.0, and I'm getting undefined function for expect.addSnapshotSerializer.

[Timer]

Looks like addSnapshotSerializer was added in Jest 19 which will be out in one of our 0.10 alpha releases, and (for sure) the stable.