jest

Event listener leak in Jest tests

MaxListenersExceededWarning.*test|memory leak.*detected.*test

Fixes

1.Remove event listeners in afterEach or component cleanup
2.Use --detectOpenHandles flag to identify what's keeping tests alive
3.Ensure server/socket connections opened in tests are closed in afterAll

jestmemory-leakcleanup

Related Errors

Jest assertion value mismatch

expect\(received\)\.toBe\(expected\)|Expected.*Received

•Check expected vs actual values — use .toEqual() for objects instead of .toBe()
•For floating point, use .toBeCloseTo() instead of exact equality

Jest mock function not called as expected

Expected.*mock.*to have been called|not been called|toHaveBeenCalled

•Verify the mock is injected correctly — check the module path in jest.mock()
•Ensure the code path that calls the function is actually reached

Jest async test timeout

Exceeded timeout.*Async callback|exceeded.*5000.*ms|jest.*timeout

•Ensure async functions resolve: await the promise or call done()
•Increase timeout: jest.setTimeout(10000) or third arg to it()