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Discussion on: Make your Angular tests 1000% faster by switching from Karma to Jest

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sherlock1982 profile image
Nikolai Orekhov

What am i doing wrong? :-) Angular 9 app + 400 tests approx, 8 core CPU.
Karma runs in ~1m 20sec
Jest runs in ~40sec.

That makes Jest two times faster but:

  1. It runs multiple node instances and takes all my CPU power. Literally I can't run anything else. The reason i think it's forced to compile multiple times because of many node instances.

  2. I can't run some of my tests in Jest because they depend on WebRTC and i can hardly mock it. There's a small number of failed tests in Jest that i need to review as well.

That doesn't look like an ultimate solution for everybody.

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dylanwatsonsoftware profile image
Dylan Watson Author

Hmm yep I think thats definitely fair. Due to the fact that Jest runs jsdom and not a real browser, there is definitely some things it won't be able to test properly, I suppose WebRTC is one of them.

I have seen some issues in the jest github repo recently about jest slowing down in recent versions.. perhaps its related?

If you are having issues with speed you could try running sequentially: jestjs.io/docs/en/troubleshooting#...