Python mock side_effect or return_value dependent on call_count

Python mock side_effect or return_value dependent on call_count

You can use the side_effect parameter of the unittest.mock.Mock object to make it return different values depending on the call count. To do this, you can define a function that takes the call count as an argument and returns the desired values based on that count. Here's an example:

from unittest.mock import Mock # Define a function to be used as a side_effect def custom_side_effect(call_count): if call_count == 1: return "First Call" elif call_count == 2: return "Second Call" else: return "Subsequent Call" # Create a mock object with the custom_side_effect function mock_obj = Mock(side_effect=lambda *args, **kwargs: custom_side_effect(mock_obj.call_count)) # Use the mock in your testing code print(mock_obj()) # First Call print(mock_obj()) # Second Call print(mock_obj()) # Subsequent Call print(mock_obj()) # Subsequent Call

In this example, we define the custom_side_effect function, which takes the call count as an argument and returns different values based on the call count. We then create a mock object mock_obj and set its side_effect to a lambda function that calls custom_side_effect with the current call count of the mock.

When you call mock_obj(), it will return values based on the call count. The first call returns "First Call," the second call returns "Second Call," and subsequent calls return "Subsequent Call."

This approach allows you to customize the return values of a mock object based on the number of times it has been called during your test cases.

Examples

  1. How to set side_effect in Python mock based on call_count?

    • Description: This query discusses how to use side_effect in a unittest.mock mock object to return different values based on the number of times a method is called.
    from unittest import mock def some_function(): pass # To be mocked # Set `side_effect` based on `call_count` with mock.patch("__main__.some_function") as mocked_function: side_effects = ["first_call", "second_call", "third_call"] mocked_function.side_effect = lambda: side_effects[mocked_function.call_count - 1] assert some_function() == "first_call" assert some_function() == "second_call" assert some_function() == "third_call"

  2. How to mock a function in Python with different return_value based on call count?

    • Description: This query discusses how to use a lambda function to control the return_value of a mocked function based on its call_count.
    from unittest import mock def another_function(): pass # To be mocked # Set different `return_value` based on `call_count` with mock.patch("__main__.another_function") as mocked_function: mocked_function.return_value = lambda: f"call {mocked_function.call_count}" assert another_function() == "call 1" assert another_function() == "call 2" assert another_function() == "call 3"

  3. How to set mock side_effect based on function arguments and call_count in Python?

    • Description: This query explores using a lambda function for side_effect to determine the return value based on function arguments and call_count.
    from unittest import mock def function_with_args(x): pass # To be mocked # Set `side_effect` based on arguments and `call_count` with mock.patch("__main__.function_with_args") as mocked_function: mocked_function.side_effect = lambda x: f"value_{x}_{mocked_function.call_count}" assert function_with_args(1) == "value_1_1" assert function_with_args(2) == "value_2_2" assert function_with_args(1) == "value_1_3"

  4. How to use mock side_effect to raise exceptions based on call_count in Python?

    • Description: This query discusses setting side_effect to raise exceptions depending on the number of times a mocked function is called.
    from unittest import mock def error_prone_function(): pass # To be mocked # Set `side_effect` to raise exceptions based on `call_count` with mock.patch("__main__.error_prone_function") as mocked_function: mocked_function.side_effect = [ "No error", RuntimeError("Second call failed"), "No error" ] assert error_prone_function() == "No error" try: error_prone_function() # This should raise the exception except RuntimeError as e: assert str(e) == "Second call failed" assert error_prone_function() == "No error"

  5. How to use mock side_effect with predefined values and track call_count in Python?

    • Description: This query discusses how to set side_effect with a predefined list of return values while keeping track of call_count.
    from unittest import mock def predefined_function(): pass # To be mocked # Use `side_effect` with predefined values with mock.patch("__main__.predefined_function") as mocked_function: mocked_function.side_effect = ["first_result", "second_result", "third_result"] assert predefined_function() == "first_result" assert predefined_function() == "second_result" assert predefined_function() == "third_result" assert mocked_function.call_count == 3

  6. How to set mock side_effect to return different results based on call_count in Python?

    • Description: This query discusses how to set side_effect with different results based on call_count.
    from unittest import mock def random_result_function(): pass # To be mocked # Use `side_effect` to return different results with mock.patch("__main__.random_result_function") as mocked_function: mocked_function.side_effect = [ "Result A", "Result B", "Result C" ] assert random_result_function() == "Result A" assert random_result_function() == "Result B" assert random_result_function() == "Result C"

  7. How to use mock side_effect to repeat certain values based on call_count in Python?

    • Description: This query discusses how to set side_effect to repeat a certain pattern of return values based on call_count.
    from unittest import mock def repeating_pattern_function(): pass # To be mocked # Use `side_effect` to repeat values based on a pattern with mock.patch("__main__.repeating_pattern_function") as mocked_function: mocked_function.side_effect = ["A", "B", "C"] * 2 # Repeats twice assert repeating_pattern_function() == "A" assert repeating_pattern_function() == "B" assert repeating_pattern_function() == "C" assert repeating_pattern_function() == "A" # Repeats the pattern

  8. How to use mock side_effect to return incremented values based on call_count in Python?

    • Description: This query explores using a lambda function in side_effect to return incremented values based on call_count.
    from unittest import mock def incrementing_function(): pass # To be mocked # Use `side_effect` to return incrementing values with mock.patch("__main__.incrementing_function") as mocked_function: mocked_function.side_effect = lambda: mocked_function.call_count assert incrementing_function() == 1 assert incrementing_function() == 2 assert incrementing_function() == 3

  9. How to use mock side_effect to simulate an asynchronous response based on call_count in Python?

    • Description: This query discusses how to set side_effect to simulate different asynchronous responses based on call_count.
    import asyncio from unittest import mock async def async_response_function(): pass # To be mocked # Use `side_effect` to simulate asynchronous responses with mock.patch("__main__.async_response_function") as mocked_function: future1 = asyncio.Future() future2 = asyncio.Future() future1.set_result("First Response") future2.set_result("Second Response") mocked_function.side_effect = [future1, future2] assert await async_response_function() == "First Response" assert await async_response_function() == "Second Response"

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