Added ability to configure Jest via package.json

[danjamin]

• works when NOT ejected by merging default and app Jest options
• eject simply combines app and default into a single package.json jest field

fixes #1785

Verified against my own project via npm link commands. I added a jest config within my package.json, ran CI=true npm test and verified that it was using my extra configuration options. I also ejected locally to make sure that worked properly and it did, resulting in a package.json with the merged options in the jest field. I am open to advice on how else to test this feature.

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla - and if you have received this in error or have any questions, please drop us a line at cla@fb.com. Thanks!

If you are contributing on behalf of someone else (eg your employer): the individual CLA is not sufficient - use https://developers.facebook.com/opensource/cla?type=company instead. Contact cla@fb.com if you have any questions.

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[gaearon]

It looks like #1830 was earlier so I’ll build on top of that.
Thanks for PR though!

[danjamin]

@gaearon is there a plan in place / a PR in the works already to enable overriding of the testResultsProcessor? This is the option I personally would like to override in my projects. Should be as simple as adding it here.

[gaearon]

I don’t think it’s a good idea to override it in Jest config—how would you run tests locally?
(I haven’t tried it so I don’t know.)

My impression is you should just pass it as an argument at CI, e.g.

  "test:ci": "react-scripts test -- --testResultsProcessor myprocessor

and then run that instead of npm test on CI.

[danjamin]

@gaearon this approach worked! Thanks for the pointer. Quick thing though, I ended up doing this:

"test:ci": "react-scripts test --testResultsProcessor=jest-junit"

after installing jest-junit and configuring it separately.

[gaearon]

Cool, thanks!