python type_error ai_generated true

AssertionError: Expected call: mock_function(1, 2, 3) Actual call: mock_function(1, 2, 4)

ID: python/unittest-mock-assert-called-with-argument-mismatch

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80%Fix Rate
88%Confidence
0Evidence
2024-01-20First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.8 active — — —
3.9 active — — —
3.10 active — — —

Root Cause

The mock object was called with arguments that do not match the expected arguments specified in assert_called_with or similar assertion methods, often due to a slight difference in data or logic in the code under test.

generic

中文

模拟对象被调用时使用的参数与assert_called_with等断言方法中指定的预期参数不匹配，通常是由于被测代码中的数据或逻辑略有差异。

Workarounds

  1. 90% success Debug the code under test to understand why arguments differ, then adjust the test or fix the code 
    Add print statements or use a debugger to inspect the actual arguments passed to the mock. For example: mock_function.assert_called_with(1, 2, 3) but if it fails, check the actual call via mock_function.call_args.
  2. 80% success Use `assert_called_once_with` with flexible matchers like `unittest.mock.ANY` or custom matchers for acceptable variations 
    from unittest.mock import ANY
mock_function.assert_called_once_with(1, 2, ANY)
This allows the third argument to be anything, but still verifies the first two.

Dead Ends

Common approaches that don't work:

  1. Changing the expected arguments to match the actual call without investigating why the code under test produces different values 70% fail

    This masks the real issue in the code under test, potentially allowing bugs to go undetected.

  2. Using `assert_any_call` instead of `assert_called_with` to ignore argument differences 50% fail

    This weakens the test by not verifying the exact arguments, which may hide important regressions.