python type_error ai_generated true

TypeError: 'NoneType' object is not callable when using mock.assert_called_with

ID: python/unittest-mock-assert-called-with-typeerror

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80%Fix Rate
82%Confidence
0Evidence
2024-05-20First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.9 active — — —
3.10 active — — —

Root Cause

The mock object is not properly configured or is being replaced by a non-callable value (e.g., None) before the assertion is made.

generic

中文

模拟对象未正确配置，或在断言之前被非可调用值（例如 None）替换。

Workarounds

  1. 85% success Ensure the mock is created with 'autospec=True' to maintain callable signature. 
    mock = unittest.mock.MagicMock(autospec=True); mock.assert_called_with(args)
  2. 80% success Verify the mock is not overwritten by using patch with return_value set explicitly. 
    with unittest.mock.patch('module.function', return_value=mock_callable): ...

Dead Ends

Common approaches that don't work:

  1. Adding more mock assertions without checking mock creation 90% fail

    The core issue is the mock object itself; additional assertions will fail similarly.

  2. Using patch decorator incorrectly and assuming mock is automatically callable 75% fail

    If patch replaces the object with a non-callable, the mock will not be callable.