jest

Jest mock not properly initialized

Cannot.*read.*property.*mockImplementation|mockReturnValue.*undefined

Fixes

1.Ensure jest.mock() path exactly matches the import path in source code
2.Use jest.fn() to create mock functions before assigning mockReturnValue
3.Check __mocks__ directory structure mirrors the module path exactly

jestmocksinitialization

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()