Test fixture creation

Provides reusable test data to multiple test functions without duplication.

When you need a shared data structure across multiple tests; when setting up test fixtures for parametrized tests; when isolating test setup from test logic.

Python test suites using pytest; commonly in unit testing, integration testing, and CI pipelines.

@pytest.fixture def ;: return ;

@pytest.fixture def ;: return ;

fixture_name: identifier, returned_value: expression (e.g., dict, list, object)

• test functions using the fixture as parameter
• @pytest.mark.parametrize
• assert statements

• returning a list
• returning a class instance
• using yield for teardown

forgetting the decorator, returning mutable objects that cause test interference, using fixture name that conflicts with builtins

@pytest.fixture with params (parametrized fixture) vs simple fixture; unittest.setUp vs pytest fixture

Coming from unittest: may expect setUp/tearDown methods; forgetting that fixtures are functions returning values.

• pytest fixtures
• test setup patterns
• arrange-act-assert

Fixtures are scoped (function, class, module, session) by default function scope; returning mutable objects can lead to side effects unless copied; use yield for cleanup.

Ensures consistent test setup, reduces boilerplate, improves test isolation.

Think of a fixture as a 'test data factory' decorated with @pytest.fixture.

Ideal for static test data; for mutable data, return a deep copy or use a factory pattern to prevent test interference.

Using fixture with parameters and yield for teardown to manage resource setup and cleanup.