Heya @JReinhold I've just stumbled across this whilst trying to set this up to speed up our CI builds. I had assumed this was already an option as it's listed in the docs (https://facebook.github.io/jest/docs/en/configuration.html#cachedirectory-string).

Would you happen to know how it got there without this being merged?

If it means anything, this will be super helpful for us. Not just for the CI speed up, but because we are trying to debug a really painful edgecase to do with transformers that only occurs in CI and only very occasionally, this will help us zip up the cached transformed files and upload to s3 when it fails.

Oh.. To make this even stranger, I found this because it looked like it wasn't working for me locally but it turned out it did work, my editor was just not indexing node_modules

  cacheDirectory: 'node_modules/.jest-cache',

$ yarn jest --showConfig

$ /Users/lbatchelor/src/atlaskit-mk-2/node_modules/.bin/jest --showConfig
{
  "config": {
    "automock": false,
    "browser": false,
    "cache": true,
    "cacheDirectory": "/Users/lbatchelor/src/atlaskit-mk-2/node_modules/.jest-cache",
    "clearMocks": false,

And sure enough, I can see the cache in that directory.

Tested in CI and got pretty great results too! (6:55min -> 2:25min to run around 6k tests)

I'm using

yarn 1.3.2
node 8.5.0
jest 20.0.4
jest-cli 20.0.4

if that helps.

@lukebatchelor this might be a stupid question, but do you realize that this is a PR for create-react-app itself, and doesn't have anything to do with jest? Are you using create-react-app or are you just using jest? The reason I'm asking, is that it seems rather strange to me that you can actually make cacheDirectory work without getting any errors, because it doesn't work right now in create-react-app, however when just using plain jest it should work out of the box.
If you are in fact using create-react-app then you've probably come to the right place, and posting your package.json and relevant CI script could make it easier to figure out what's going on.

You are 1000% correct. I was very confused, hahaha. Thanks!