jest

Jest spy on non-existent or non-function property

Cannot spy.*property.*not a function|spyOn.*undefined

Fixes

1.Verify the method name exists on the object being spied on
2.For getters/setters, use jest.spyOn(obj, 'prop', 'get')
3.Ensure the module is imported before spying — mock at the top level

jestspymocks

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()