Streaming individual test results

[SimenB]

🚀 Feature Proposal

Right now we collect test results from a whole suite before passing it to a testResultsProcessor (and printing it). I'd like to also be able to know as each individual test completes without waiting for the whole suite.

Motivation

2 use cases comes to mind:

1. IDEs and other reporters are able to display individual test results as they come in, instead of waiting for the whole suite
2. Tracking down which test hangs a test suite (see Upgrade jest webpack/webpack#7311 which just hangs - seeing the last completed test would be great)

As a bonus to the last point, we might want to stream multiple states per test - pending, running and complete or something might make sense.

Example

Not really sure how it would be used. I guess an extra method in the reporter? Might make sense as part of Jest Hooks? https://github.com/facebook/jest/blob/master/packages/jest-cli/src/jest_hooks.js

Pitch

The UI for it does not have to live within Jest, but we should power custom reporters and test result processors to display real time data about a test suite

[SimenB]

Now that I've gotten a primer on jest-circus, I guess this can be closed. It'll work out of the box (as long as one does not have an afterAll which the suite will have to wait for).

#4471 is pretty much the same thing anyways, so closing.

[aaronabramov]

@SimenB those are still two different reporting mechanisms:

1. reporting in jest via different reorters "coverage, default, summary, etc."
2. sending flux actions within jest-circus - that has no way outside its current vm though

afterAll shouldn't be a problem any more, we chose to not fail any individual tests, but rather throw a global error that'll fail the whole suite

[SimenB]

Would it be possible to emit events from jest-circus outside of the vm as well?

[aaronabramov]

yes, but it'll introduce the whole world of parallelism, since we'll be running a lot of tests in parallel, the events will need to be handled differently :)

[SimenB]

Good point. Namespacing in test file name or something (maybe combined with runner?) might be enough?

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