pytest-mock for enhanced mocking - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a pytest-mock patch usage

What is the output of this pytest test when run with pytest-mock?

PyTest

import requests

def fetch_data():
    response = requests.get('https://api.example.com/data')
    return response.status_code

def test_fetch_data(mocker):
    mock_get = mocker.patch('requests.get')
    mock_get.return_value.status_code = 404
    result = fetch_data()
    print(result)

A 404

B 200

C AttributeError

D None

💡 Hint

The mock replaces requests.get and sets the status_code attribute.

The mocker.patch replaces requests.get with a mock object. Setting return_value.status_code to 404 means fetch_data returns 404.

❓ assertion

intermediate

Correct assertion to verify mock call count

Which assertion correctly verifies that the mocked function was called exactly twice?

PyTest

def test_calls(mocker):
    mock_func = mocker.Mock()
    mock_func()
    mock_func()
    # Which assertion below is correct?

A assert mock_func.call_count() == 2

B assert mock_func.called == 2

C assert mock_func.call_args == 2

D assert mock_func.call_count == 2

💡 Hint

Check the attribute that counts calls on a mock object.

The call_count attribute holds the number of times the mock was called. It is an integer, so assert mock_func.call_count == 2 is correct.

🔧 Debug

advanced

Identify the error in mock patching

Why does this test raise an AttributeError when run?

PyTest

import mymodule

def test_func(mocker):
    mocker.patch('mymodule.nonexistent_function')
    mymodule.nonexistent_function()

A AttributeError because 'nonexistent_function' does not exist in mymodule

B SyntaxError due to missing colon

C TypeError because patch requires a callable

D No error, test passes

💡 Hint

Check if the target to patch exists in the module.

Patching a non-existing attribute causes AttributeError because the patch target must exist.

❓ framework

advanced

pytest-mock fixture usage in test functions

Which statement about the pytest-mock fixture 'mocker' is true?

A The 'mocker' fixture automatically patches all functions without explicit use

B The 'mocker' fixture must be included as a test function argument to use it

C The 'mocker' fixture can only patch functions in the standard library

D The 'mocker' fixture requires manual import in each test file

💡 Hint

Think about how pytest fixtures are injected.

pytest fixtures like 'mocker' are injected by including them as parameters in test functions.

🧠 Conceptual

expert

Best practice for mocking external API calls with pytest-mock

Which approach best ensures tests using pytest-mock remain reliable and isolated when mocking external API calls?

A Patch the external API URL string to a local server address

B Avoid mocking and always make real HTTP requests during tests for accuracy

C Patch the exact function that makes the HTTP request in the module under test, not the external library directly

D Patch the external library's HTTP request function globally in conftest.py for all tests

💡 Hint

Consider test isolation and minimizing side effects.

Patching the function in the module under test avoids affecting other tests and keeps mocks focused and reliable.