Mocking and Spying Multiple Functions with Pytest-mock

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What will you learn?

In this tutorial, you will master the art of using Pytest-mock to effortlessly mock and spy on multiple functions simultaneously. By the end of this guide, you will have a firm grasp on how to efficiently utilize Pytest-mock for effective testing practices.

Introduction to the Problem and Solution

When dealing with intricate Python code, the necessity to mock or spy on multiple functions concurrently arises frequently. This enables us to focus on specific sections of our code during testing without impacting other components. Pytest-mock stands out as a robust library that seamlessly integrates with pytest, offering convenient features for mocking and spying on functions effectively.

To address the challenge of mocking and spying on multiple functions, we can harness the capabilities of Pytest-mock. By mastering the techniques to employ Pytest-mock proficiently, we can effortlessly create mocks and spies for various functions within our Python codebase during testing.

Code

import pytest
from unittest.mock import Mock

def func1():
    return 1

def func2():
    return 2

@pytest.fixture
def mocked_functions(mocker):
    mocker.patch('__main__.func1', Mock(return_value=100))
    mocker.patch('__main__.func2', Mock(side_effect=lambda: 'spy'))

def test_mocked_functions(mocked_functions):
    assert func1() == 100
    assert func2() == 'spy'

# Copyright PHD

Note: Replace __main__ in the patch statements with your actual module name.

Explanation

The provided code snippet works as follows: – Definition of two simple functions func1 and func2. – Creation of a fixture named mocked_functions, utilizing Pytest-mock’s mocker object. – Patching of both func1 and func2 within this fixture to specify their behavior during testing. – Verification in the test function test_mocked_functions ensures that the patched versions behave as intended.

By combining fixtures with Pytest-mock’s functionalities, we can effectively mock and spy on multiple functions in tests while maintaining clarity and readability.

    How do I install pytest-mock?

    You can install pytest-mock via pip by executing:

    pip install pytest-mock

# Copyright PHD

    Can I use pytest fixtures with pytest-mock?

    Yes, you can create fixtures that leverage pytest-mocks capabilities for mocking objects/functions in your tests.

    Is it possible to mock class methods with pytest-mock?

    Certainly! You can utilize pytest-mocks patch method to mock both class methods and standalone functions.

    What is the difference between mocking and spying in testing?

    Mocking replaces a function/object with a fake implementation for testing, while spying allows observation of calls made to a function/object without directly affecting its behavior.

    Can I combine mocking and spying in a single test case?

    Absolutely! You can blend both techniques based on your testing needs within a single test case using Pytest-Mock.

    Conclusion

    To summarize, harnessing Pytest alongside pytest–mock empowers seamless unit-testing practices by facilitating mocking & spying functionalities across numerous functions, ensuring reliability & resilience throughout Python application development cycles.

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