jest --watch (option "o") tests all files even if only one file is changed

[ffxsam]

• Mac OS 10.12.3
• jest 18.1.0
• node 6.9.4
• npm 4.1.2

When running npm test -- --watch and hitting 'o' to test only updated files, all files get tested even if only one is modified.

Repo: https://github.com/ffxsam/jest-watch-strangeness

Clone and run npm install, then npm test -- --watch. Open up imports/features/SomeFeature/components/Thing/Thing.js and, for example, modify line 7. Tests for Thing.js and Whatever.js both get run.

[cpojer]

The changed files only mode is "best-effort". Sometimes Jest cannot accurately predict what the dependency graph will look like. In this case, I think you might have either had a local change that triggered this (like a change to Radium or something) or that there is some other confusion.

[javiercr]

I'm struggling with the same problem, every time all my tests are run no matter which file I change.

I've trying to figure out how Jest decides what tests to run but I couldn't find anything in the docs. @cpojer is this explained somewhere? Some sort of guidance on how to help Jest to determine which tests has to run would be very helpful.

PS: thank you for Jest, it's amazing!

[javiercr]

I just found out thanks to this video that Jest seems to use git head to figure out which tests has to run. After committing some of my changes I now see that only some tests are run (with option "o").

[jardakotesovec]

@cpojer I think still would be handy to have explanation how jest attempts to solve it, so maybe we could avoid some patterns to not confuse jest.

[accimeesterlin]

Try this
brew uninstall watchman
brew link automake
brew install --HEAD watchman

Happy coding

[joetidee]

I'm having the same issue. I run tests using:

jest --watch --notify

and it runs tests that are completely unrelated to to the file that has changed. This is really annoying as one suite is particularly slow, which means even if I am testing one file which has a small associated test it will run the slow suite every time. How to fix this?

[ferico55]

have you tried to clear the watchman?
watchman watch-del-all
and try to run jest again jest --watch

[nickofthyme]

I had this issue when changing high-level config files (i.e. tsconfig.json). Jest would not be able to tell how those changes affected individual tests so it rightfully reruns all tests.