Problem

When your Jest tests used to pass but suddenly started to fail, this may be related to cache.

In my case, the test coverage was reporting uncovered lines. When I cleared my Jest cache, the tests passed again.

Solution

To clear cache with Yarn:

yarn jest --clearCache

Output:

yarn run v1.9.4
./node_modules/.bin/jest --clearCache
Cleared /var/folders/c8/hg7gtddj49qgpvghtv2grkp9j21wxz/T/jest_r86htr
✨  Done in 0.54s.

Or with npx:

npx jest --clearCache