pytest — The Python Testing Framework That Scales

What pytest Does

• Auto-discovery — finds test_*.py files and test_* functions
• Assertion introspection — plain assert with detailed failure diffs
• Fixtures — DI for test setup/teardown (function, class, module, session scope)
• Parametrize — run same test with multiple inputs
• Markers — @pytest.mark.slow, @pytest.mark.skip, custom
• Plugins — 1200+ on PyPI (pytest-cov, pytest-xdist, pytest-mock, pytest-asyncio)
• Conftest — shared fixtures across test directories
• Temporary directories — tmp_path fixture
• Capture — stdout/stderr capture per test
• Parallel — via pytest-xdist

Comparison

FAQ

Q: pytest vs unittest? A: pytest is more concise (no class needed), with better assertions (no assertEqual) and a stronger fixture DI. The vast majority of new Python projects use pytest.

Q: How to test async code? A: pip install pytest-asyncio, then use @pytest.mark.asyncio async def test_xxx() to await async functions.

Q: Fixture scope? A: function (once per test), class, module, session (once for the entire test run). Larger scope means lower setup overhead but weaker isolation.

Sources

• Docs: https://docs.pytest.org
• GitHub: https://github.com/pytest-dev/pytest
• License: MIT