Fixture dependencies (fixture using fixture) in PyTest - Build an Automation Script

Test fixture dependency using pytest fixtures

Preconditions (2)

Step 1: Create a fixture named 'db_connection' that returns a string 'db_connected'

Step 2: Create another fixture named 'user_data' that uses 'db_connection' fixture and returns a dictionary {'user': 'test_user', 'status': 'active'}

Step 3: Write a test function 'test_user_status' that uses 'user_data' fixture

Step 4: Inside the test, assert that 'user_data' dictionary has key 'status' with value 'active'

Step 5: Run the test using pytest

✅ Expected Result: The test passes successfully, confirming that the fixture 'user_data' correctly uses the 'db_connection' fixture and provides expected data

Automation Requirements - pytest

Assertions Needed:

Assert that 'status' key in 'user_data' fixture equals 'active'

Best Practices:

Use fixture dependency by passing one fixture as parameter to another

Use descriptive fixture names

Keep fixtures simple and focused

Use pytest's assert statements for clarity

Avoid hardcoding values inside tests; use fixtures for setup

Automated Solution

PyTest

import pytest

@pytest.fixture
def db_connection():
    # Simulate database connection setup
    return 'db_connected'

@pytest.fixture
def user_data(db_connection):
    # Use db_connection fixture to prepare user data
    return {'user': 'test_user', 'status': 'active'}

def test_user_status(user_data):
    assert user_data['status'] == 'active'

The db_connection fixture simulates setting up a database connection and returns a string.

The user_data fixture depends on db_connection by accepting it as a parameter. This shows fixture dependency.

The test function test_user_status uses the user_data fixture and asserts that the user status is 'active'.

This structure keeps setup code reusable and clean, demonstrating how one fixture can use another.

Common Mistakes - 3 Pitfalls

{'mistake': 'Not passing the dependent fixture as a parameter to the fixture that needs it', 'why_bad': "The fixture dependency won't work and the dependent fixture won't receive the needed setup, causing errors or incorrect test data.", 'correct_approach': 'Always include the dependent fixture as a parameter in the fixture function definition.'}

Using print statements instead of assertions in tests

Hardcoding setup data inside test functions instead of fixtures

Bonus Challenge

Now add a third fixture 'admin_user_data' that depends on 'db_connection' and returns {'user': 'admin', 'status': 'active', 'role': 'admin'}. Write a test to verify the 'role' is 'admin'.

Show Hint