Jest worker process crashed unexpectedly

What this failure means

A Jest worker process crashed mid-test run. Jest spawns multiple worker processes to run tests in parallel, and one of them exited unexpectedly.

Symptoms

Faultline looks for one or more of these log fragments:

A worker process has quit unexpectedly
Jest worker exited
Force exiting Jest
jest-worker
Worker failed after
worker crashed
The worker has exited.
jest-circus

Diagnosis

A Jest worker process crashed mid-test run. Jest spawns multiple worker processes to run tests in parallel, and one of them exited unexpectedly.

Fix steps

1. Run with a single worker to isolate the failing test: jest --runInBand.
2. Identify which suite crashes first by running Jest in-band with verbose output.
3. If a native addon is involved, rebuild it for the current Node version.
4. If the crash is memory-related, increase Node memory with NODE_OPTIONS=--max-old-space-size=4096.
5. Search the test code for process.exit() or process.abort() calls.

Validation

• jest --runInBand completes without a worker crash.
• Re-run the CI test job and confirm the worker stays alive through the suite.

Why it matters

Jest worker crashes are commonly caused by a native Node addon segfaulting inside a worker, a test consuming too much memory, a process.exit() call in test code, or a Jest and Node version mismatch.

Prevention

• Set maxWorkers explicitly in jest.config.js for CI runners with tight memory limits.
• Audit test files for process-terminating calls.
• Keep Jest and Node versions aligned across local and CI environments.

Try it locally

jest --runInBand
jest --runInBand

How Faultline detects it

Use faultline explain jest-worker-crash to see the full playbook.

faultline analyze build.log
faultline explain jest-worker-crash

Generated from playbooks/bundled/log/test/jest-worker-crash.yaml. Do not edit directly.