pytest-patterns

Pytest fixtures in conftest.py provide centralized test setup by defining reusable functions across your test suite. This pattern isolates initialization logic, ensuring consistent test preconditions and reducing code duplication.

The best way to run multiple input scenarios in pytest is using the @pytest.mark.parametrize decorator. It executes a single test function against defined argument sets, generating distinct test cases for each input combination automatically.

You select specific tests in pytest by applying custom markers like @pytest.mark.slow to test functions. This allows targeted execution via command-line selection, isolating slow tests or grouping tests by feature without modifying test logic.

To assert exceptions and floating point values in pytest, use pytest.raises to verify expected errors and pytest.approx for numerical comparisons. These assertions ensure your tests fail gracefully on unexpected exceptions and handle float precision accurately.

Organizing pytest test files follows standard conventions where test files start with test_ and reside in dedicated directories. Applying these structural patterns alongside fixtures and markers improves test discoverability and suite maintainability.