Python Testing Patterns

Generate focused, behavior-driven tests with pytest. Prioritize observable behavior over implementation details. For framework configuration (pyproject.toml, plugins, CI), see references/framework-config.md. For deep conftest patterns and heavy-dep mocking, see references/pytest-infrastructure.md. For full TDD discipline, see references/tdd-best-practices.md.

1. Test Philosophy

What to test

• Observable behavior and return values
• User-facing workflows and API contracts
• Edge cases and error handling at system boundaries
• State transitions and side effects
• Data validation and transformation rules

What NOT to test

• Framework internals (pytest, SQLAlchemy, FastAPI mechanics)
• Implementation details (private methods, internal variable names)
• Third-party library behavior
• Simple utility functions with no branching logic
• That objects are truthy -- this asserts nothing useful