Memory Leak on ridiculously simple repo

You guys do an awesome job and we all appreciate it! 🎉

🐛 Bug Report

On a work project we discovered a memory leak choking our CI machines. Going down the rabbit hole, I was able to recreate the memory leak using Jest alone.

Running many test files causes a memory leak. I created a stupid simple repo with only Jest installed and 40 tautological test files.

I tried a number of solutions from https://github.com/facebook/jest/issues/7311 but to no avail. I couldn’t find any solutions in the other memory related issues, and this seems like the most trivial repro I could find.

Workaround 😢

We run tests with --expose-gc flag and adding this to each test file:

afterAll(() => {
  global.gc && global.gc()
})

To Reproduce

Steps to reproduce the behavior:

git clone [e-mail]:javinor/jest-memory-leak.git
cd jest-memory-leak
npm i
npm t

Expected behavior

Each test file should take the same amount of memory (give or take)

Link to repl or repo (highly encouraged)

https://github.com/javinor/jest-memory-leak

Run npx envinfo --preset jest

Paste the results here:

System:
    OS: macOS High Sierra 10.13.6
    CPU: (4) x64 Intel(R) Core(TM) i7-5557U CPU @ 3.10GHz
  Binaries:
    Node: 10.15.0 - ~/.nvm/versions/node/v10.15.0/bin/node
    Yarn: 1.12.3 - /usr/local/bin/yarn
    npm: 6.4.1 - ~/.nvm/versions/node/v10.15.0/bin/npm
  npmPackages:
    jest: ^24.1.0 => 24.1.0

[javinor]

Quick Recap

• Good - Running tests with jest@23 works as expected - heap size oscillates but goes down to original - it appears like the GC is succeeding to collect all memory allocated during the tests
• Bad - Running tests with jest@24+ including jest@26.6.3 - heap size continues to grow over time, oscillating, but doesn’t seem to go down to the initial size - My assumption is that there’s a memory leak preventing GC for freeing up all the memory
• I took the screenshots after running @jaredjj3’s example repo - see this comment)

@SimenB help? 🙏

Running with jest@23

Running with jest@26

[fyodorvi]

Similar here, jest + ts-jest, simple tests get over 1GB of memory and eventually crash.