jest --changedSince=origin/master

[alsuren]

Summary

This is a duplicate of #5188 on the off-chance that the CI server's cache per-PR, and is therefore only poisoned for that PR.

I often have jest --watch running in a window, but sometimes I forget to look at it before committing, or I stage a bunch of changes that break tests, and it hides them from the test runner. This means that I often get surprised by CI test failures when I come to open pull requests.

This change allows you to write jest --watch --changedFilesToContributeTo=origin/master to test your entire feature branch, but not the whole project. It also tests only your changes if your branch has diverged from origin/master.

Test plan

~/src/jest$ yarn jest --listTests | wc -l
     220
~/src/jest$ yarn jest --listTests --changedFilesToContributeTo=origin/master | wc -l
      12

[codecov-io]

Codecov Report

Merging #5312 into master will decrease coverage by <.01%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master    #5312      +/-   ##
==========================================
- Coverage   61.32%   61.32%   -0.01%     
==========================================
  Files         205      205              
  Lines        6909     6914       +5     
  Branches        4        4              
==========================================
+ Hits         4237     4240       +3     
- Misses       2671     2673       +2     
  Partials        1        1

Impacted Files	Coverage Δ
packages/jest-config/src/normalize.js	93.1% <ø> (ø)	⬆️
packages/jest-config/src/valid_config.js	100% <ø> (ø)	⬆️
packages/jest-config/src/index.js	25.92% <ø> (ø)	⬆️
packages/jest-cli/src/get_changed_files_promise.js	100% <ø> (ø)	⬆️
packages/jest-changed-files/src/hg.js	28.12% <0%> (-1.88%)	⬇️
packages/jest-changed-files/src/git.js	94.44% <100%> (+0.5%)	⬆️

---

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[SimenB]

This needs a rebase.

Also, copying over my comment from the other PR.

--changedFilesToContributeTo is pretty verbose, what about just --changedSince?

[SimenB]

can you move this to just below master?

[SimenB]

Can you add a "Since Jest 22.1.3+" or something?

[alsuren]

I said 22.2.0 because announcing that a feature is available since a patch release makes me uneasy. If it turns out that we release this feature without bumping the minor version then then ##### available in Jest **22.2.0+** is still not strictly a lie ;-)

[SimenB]

Couple of docs nits, no biggie.

Thank you so much for adding this! Cool feature

[SimenB]

Question: If I say --changedSince=HEAD and then make a commit, would this then know what changed, or do I have to do something like --changedSince=`git rev-parse HEAD` in order to be able to commit and still test all changes since I started?

[alsuren]

Thanks for sticking with me as reviewer while I changed the spec and made a thousand rebases :D

If you say --changedSince=HEAD then git will re-evaluate what HEAD is every time, so you would indeed need to git rev-parse HEAD if you want the base point to stay put.

The flag is designed to so that you can just jest --watch --changedSince=origin/master and leave it running in the background forever (even when you switch what you're working on, or other people push things to origin/master) and it will always only test the changes that you're about to contribute.

If you just want to test the changes since the last time you did a git push, I think that --changedSince=@{upstream} should do the trick (according to man git rev-parse)

[jwbay]

Just used this for the first time, and it's awesome. Fits my workflow perfectly. Thanks @alsuren!

[github-actions]

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