Pytest

Full standards in pytest.md. Always-on summary:

File and function naming:

• Files: test_<module>.py (prefix, not suffix) — pytest discovers these automatically
• Functions: def test_<behaviour>() — describe the behaviour, not the method
• Classes: class TestUserService: — group related tests; no __init__ method

Fixtures:

• Declare with @pytest.fixture decorator in conftest.py — pytest injects them automatically by parameter name
• Use the narrowest scope needed: function (default) → class → module → session
• Yield fixtures for setup/teardown: yield provides the value; cleanup runs after

Parametrize:

• @pytest.mark.parametrize for testing multiple inputs — never copy-paste tests
• Use ids= for readable test names in the output

Assertions:

• Plain assert statements — pytest rewrites them for detailed output; e.g., assert response.status_code == 200
• pytest.raises(ExcType) for exception testing — use as context manager
• pytest.approx() for floating-point comparisons

Output capture:

• Use the capsys fixture to capture and assert on stdout/stderr — never write raw stdout in tests

Never:

• unittest.TestCase style in new pytest code — use plain functions and fixtures
• Raw stdout debugging — use pytest -s flag or proper logging
• Skip tests without a reason: @pytest.mark.skip(reason='...') required

Related skills: backend/python-fastapi (pytest-asyncio, TestClient), database/sqlalchemy (session fixture patterns)

Source: manikumarkv/devrunway-claude-plugin — distributed by TomeVault.