[test] Make all tests runnable with React 17 #22290
Merged
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Codebase is now fully compatible with the current React 17 release candidate.
We need to wrap unmount actions in
act
due to React 17 lazily calling cleanup functions from effects. Otherwise these would be called in between tests making it incredibly hard to find out which test caused a possible error. Sometimes they would also not run at all (in JSDOM) leading intervals running forever and mocha not exiting. It's also safer to flush them in the test or hook so that tests are better isolated.