Mock call assertions in PyTest - Test Execution Trace

Test Overview

This test checks if a mocked function is called with the expected arguments. It verifies that the function was called exactly once with the correct parameters.

Test Code - pytest

PyTest

from unittest.mock import Mock
import pytest

def test_mock_call():
    mock_func = Mock()
    # Call the mock function with specific arguments
    mock_func('hello', key='value')
    # Assert the mock was called once with the expected arguments
    mock_func.assert_called_once_with('hello', key='value')

Execution Trace - 3 Steps

Step	Action	System State	Assertion	Result
1	Create a mock function object	mock_func is a Mock object with no calls recorded	-	PASS
2	Call mock_func with arguments ('hello', key='value')	mock_func records one call with arguments ('hello', key='value')	-	PASS
3	Assert mock_func was called once with ('hello', key='value')	mock_func call history matches expected arguments	mock_func.assert_called_once_with('hello', key='value') verifies call count and arguments	PASS

Failure Scenario

Failing Condition: mock_func was not called exactly once with the expected arguments

Execution Trace Quiz - 3 Questions

What does assert_called_once_with check in this test?

A That the mock was never called

B That the mock was called exactly once with the specified arguments

C That the mock was called multiple times with any arguments

D That the mock returned a specific value

Key Result

Always verify both the number of calls and the exact arguments when asserting mock calls to ensure your code interacts correctly with dependencies.