Autouse fixtures in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest autouse fixture execution order

Consider the following pytest code with autouse fixtures. What will be the output when running the test?

PyTest

import pytest

@pytest.fixture(autouse=True)
def setup_one():
    print("Setup One")

@pytest.fixture(autouse=True)
def setup_two():
    print("Setup Two")


def test_example():
    print("Test Running")

A Test Running\nSetup Two\nSetup One

B Setup One\nSetup Two\nTest Running

C Test Running\nSetup One\nSetup Two

D Setup Two\nSetup One\nTest Running

💡 Hint

Autouse fixtures run before the test function in the order they are defined.

Pytest runs autouse fixtures in the order they appear in the code before the test function. So 'setup_one' prints first, then 'setup_two', then the test prints.

❓ assertion

intermediate

Correct assertion to verify autouse fixture effect

You have an autouse fixture that appends 'setup' to a list before each test. Which assertion correctly verifies the list contains 'setup' after the test runs?

PyTest

import pytest

results = []

@pytest.fixture(autouse=True)
def add_setup():
    results.append('setup')


def test_check():
    # Which assertion below is correct?
    pass

A assert 'setup' in results

B assert results == ['setup']

C assert results.count('setup') == 0

D assert results is None

💡 Hint

The fixture adds 'setup' to the list before each test, so the list should contain 'setup'.

Option A checks if 'setup' is in the list, which is true after the fixture runs. Option A may fail if multiple tests run and append multiple 'setup' entries. Options C and D are incorrect.

🔧 Debug

advanced

Identify why autouse fixture is not running

Given this pytest code, why does the autouse fixture not run before the test?

PyTest

import pytest

@pytest.fixture(autouse=True)
def setup():
    print("Setup running")

def test_sample():
    print("Test running")

A The fixture is defined in a different module and not imported

B The fixture is missing the @pytest.mark.usefixtures decorator

C The test function name does not start with 'test_'

D Autouse fixtures only run for class-based tests

💡 Hint

Autouse fixtures must be visible to the test, usually in the same module or conftest.py.

If the fixture is defined in another module but not imported or in conftest.py, pytest won't run it automatically. The other options are incorrect because autouse fixtures do not require @usefixtures, test name is correct, and autouse works for function tests too.

❓ framework

advanced

Behavior of autouse fixtures with different scopes

Which statement correctly describes how autouse fixtures behave with different scopes in pytest?

A Autouse fixtures cannot have 'class' scope

B An autouse fixture with 'function' scope runs once per test session

C Autouse fixtures ignore their scope and always run before each test function

D An autouse fixture with 'module' scope runs once per module before any tests

💡 Hint

Fixture scope controls how often the fixture runs, autouse controls if it runs automatically.

Autouse fixtures respect their scope. A 'module' scoped autouse fixture runs once before any tests in that module. 'Function' scope runs before each test function. Option D is wrong because 'function' scope runs per test, not per session. Option D is false because scope matters. Option D is false; autouse fixtures can have 'class' scope.

🧠 Conceptual

expert

Impact of autouse fixtures on test isolation and performance

Which of the following is the best explanation of the impact of using autouse fixtures extensively in a large pytest suite?

A Using autouse fixtures eliminates the need for explicit fixture usage and has no impact on test performance

B Autouse fixtures always speed up tests by sharing setup across all tests

C Autouse fixtures improve test isolation but may slow down the test suite if they perform expensive setup for every test

D Autouse fixtures prevent tests from running in parallel

💡 Hint

Think about how often autouse fixtures run and what they do.

Autouse fixtures run automatically before tests, which helps ensure setup runs consistently, improving isolation. However, if the fixture does expensive work and has a narrow scope like 'function', it can slow down the suite. They do not inherently speed up tests or prevent parallelism.