pytest-testing_skill

Overview

This skill is a practical, hands-on guide for writing and running pytest tests in Python projects. It covers setup, test organization, fixtures, parametrization, mocking, coverage, debugging, and CI integration to help you ship reliable code. Use it to adopt pytest conventions and improve test quality quickly.

How this skill works

The guide describes how to install pytest and pytest-cov, structure test files, and configure pytest via pytest.ini or pyproject.toml. It explains fixtures, scopes, assertions, parametrized tests, mocking with unittest.mock, coverage reporting, and common debugging commands. It also shows CI examples and common fixes for import/fixture/coverage problems.

When to use it

• Setting up pytest for a new project
• Writing unit, integration, or CLI tests
• Creating and reusing fixtures and parametrized cases
• Isolating code with mocks and testing exceptions
• Measuring and improving test coverage
• Debugging failing tests and integrating with CI/CD

Best practices

• Keep tests independent; avoid global state and ordering dependencies
• Favor fixtures over globals for setup and teardown; choose appropriate fixture scopes
• Name files, classes, and functions using pytest conventions (test_*, Test*, test_*)
• Write descriptive test names and add short docstrings for intent
• Test both happy paths and edge cases, including error conditions
• Use markers (slow, integration, unit) to filter tests and keep CI fast

Example use cases

• Quickly scaffold tests: install pytest, add tests/ and pytest.ini, run pytest -v
• Create reusable fixtures in conftest.py for shared setup like DB sessions or temp files
• Parametrize input sets to validate multiple values with a single test function
• Mock external dependencies (API calls, argv) to isolate logic and assert interactions
• Run coverage locally and produce HTML or CI reports with pytest --cov and pytest-cov