jest --watch runs tests twice after chokidar accesses a file

[kumar303]

Describe the problem and steps to reproduce it:

• Start yarn test in a shell
• Start yarn flow:dev in another shell
• Edit a file

What happened?

Changing the file causes the tests to run twice.

What did you expect to happen?

The tests should only run once.

Anything else we should know?

It's happening because chokidar changes the file access time shortly after emitting a change event. I'm not sure why. Changing access time causes jest to re-run tests (see jestjs/jest#7124) which seems like a bug.

I deduced it with something like this:

stat -x src/amo/components/AddonReviewCard/index.js
chokidar src/ tests/ -c 'sleep 5 && echo "done"' --initial

I was using the p filter in jest to only run TestAddonReviewCard.js. Since this test suite is fast, it helped to see the flicker of jest running the tests twice.

We fixed a separate (I think?) but related bug in #10514