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name: Pytest description: This skill should be used when the user asks about "pytest", "writing tests", "test fixtures", "parametrize", "mocking", "test coverage", "conftest" version: 1.0.0

Pytest Testing

Guidance for writing effective tests with pytest.

Core Concepts

Fixtures

Reusable test setup/teardown. Use yield for cleanup.

Scopes:

Key concept: conftest.py makes fixtures available to all tests in directory.

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Parametrize

Test multiple inputs without repeating code.

Key concept: Generates separate test for each parameter set - failures are isolated.

Use pytest.param() for:

• Custom test IDs
• Expected failures (marks=pytest.mark.xfail)
• Conditional skips

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Markers

Tag tests for filtering and special behavior.

Custom markers: Define in pyproject.toml, run with pytest -m "marker"

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Mocking

Key concept: Patch where the thing is used, not where it's defined.

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Test Organization

Copytests/
├── conftest.py          # Shared fixtures
├── unit/                # Fast, isolated
├── integration/         # Multiple components
└── e2e/                 # Full system

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Coverage

Key thresholds:

• 80%+ is good coverage
• 100% is often overkill
• Branch coverage catches conditionals

Config in pyproject.toml: Set source, branch=true, fail_under

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Common Commands

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Best Practices

Resources

• Pytest docs: https://docs.pytest.org/
• pytest-asyncio: https://pytest-asyncio.readthedocs.io/