Jest performance is at best 2x slower than Jasmine, in our case 7x slower

🐛 Bug Report

We’ve been using Jest alongside Jasmine for the same test suite for about a year now. We love Jest because it’s developer experience is superb, however, on our very large monorepo with ~7000+ test specs, Jest runs about 7 times slower than Jasmine. This problem has been getting worse and worse as the test suite grows and as a result, we always run our test suite via Jasmine and only use Jest for development --watch mode.

We would ♥ to use Jest as our only test runner, but its poor performance is preventing us from doing so. Having to run both Jest and Jasmine runners requires painful CI setup and constant upkeep of the Jasmine environment setup (which is much more complex than Jest’s).

I’d like to better understand why the performance difference is so significant and if there’s anything that can be done to optimize it.

To Reproduce

I’ve created a very detailed project to reproduce and profile both Jest and Jasmine on the same test suite in this project: https://github.com/EvHaus/jest-vs-jasmine

The environment is the same. The configurations are very similar. Both use JSDom. Both use the same Babel setup. Additional instructions are contained therein.

Expected behavior

Running tests through Jest should ideally be as fast as running them through Jasmine.

Link to repl or repo (highly encouraged)

https://github.com/EvHaus/jest-vs-jasmine

Run npx envinfo --preset jest

Tested on a few different platform. See https://github.com/EvHaus/jest-vs-jasmine README for more info.

[Shingaz]

Same issue here on 25.2.2, file resolution takes too long. Is there any plan to speed it up?

[armano2]

i was trying to do migration from mocha to jest… and… mocha is finishing all tests before jest starts first one… i think there is somewhere issue with resolving/reading files -> my project contains ~70k files, and i’m running ~19k tests.

after some digging its looks like jest is trying to import all files from all folders before he starts tests, i’m providing explicit match for test file: testMatch: ['<rootDir>/dist/alignment.spec.js'].

i was able to run tests by adding to jest.config

modulePathIgnorePatterns: ['<rootDir>/fixtures/.*'],

but it’s still 11m… as opposed to mocha ~1m and without test framework (try/catch assert) ~40-50s

turning off transformation helped to

transform: {}

so far my configuration looks like this:

module.exports = {
  testEnvironment: 'node',
  testMatch: ['<rootDir>/dist/alignment.spec.js'],
  moduleFileExtensions: ['js'],
  transform: {},
  modulePathIgnorePatterns: ['<rootDir>/projects/.*', '<rootDir>/node_modules/.*']
};

its still slow, ~4min

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now i’m looking for way to turn of prettier, i don’t care about formatting errors…