olebedev / jest-perf-issue

This repo was made to provide a reproducible case of jest performance degradation on 25.x version with --coverage flag. See jestjs/jest#9457

How to reproduce

$ rm -rf target node_modules            # make sure you delete `target` & `node_modules`
$ yarn                                  # install node_modules
$ yarn test bin/ci/hoydenism --coverage # run the tests

Note: the master branch is pointed to jest@24.9.0, jest25 branch is pointed to jest@25.1.0.

Results

Benchmarks were ran on MBP 2019, 32Gb RAM, i9-8950HK CPU @ 2.90GHz.

jest version	branch	time
24.9.0	master	348.077s
25.1.0	jest25	591.33s