Fix 'EMFILE: too many open files' error in Jest
When I tried to run jest --watch in a codebase, I received the following error:
Error: EMFILE: too many open files, watch
at FSEvent.FSWatcher._handle.onchange (fs.js:1372:28)
Emitted 'error' event at:
at NodeWatcher.checkedEmitError (/Users/seanmcp/dev/REPO/node_modules/sane/src/node_watcher.js:143:12)
at FSWatcher.emit (events.js:182:13)
at FSEvent.FSWatcher._handle.onchange (fs.js:1378:12)
A Google search of the error message produced three (!) results. The second was a PDF from Mozilla that recommended installing watchman.
Why watchman?
Watchman is a file-watching service from Facebook that will respond to changes in your files. Jest (also by Facebook) default to using watchman in --watch mode.
Watchman is available on all major platforms. On a Mac or Linux with Homebrew installed, you can run:
brew install watchman
With that installed, Jest’s --watch flag works as expected.
I hope that works for you (and saves you some valuable time)!
Happy testing!