TDD Python Reference

Comprehensive reference materials for Python Test-Driven Development - pytest, unittest, mocking, coverage, and Python-specific testing patterns.

Available References

pytest-guide.md

Complete pytest reference - fixtures, parametrize, marks, plugins, and configuration.

When to use: Modern Python projects, learning pytest patterns Covers: Fixtures, parametrize, marks, plugins, conftest.py, pytest.ini Key Topics: Dependency injection, test discovery, assertion introspection

unittest-guide.md

Comprehensive unittest reference - TestCase classes, assertions, setUp/tearDown, test discovery.

When to use: Legacy projects, corporate environments, no external dependencies Covers: TestCase structure, assertion methods, test organization, discovery Key Topics: Class-based testing, setUp/tearDown, unittest.main()

mocking-reference.md

Complete mocking guide - Mock, MagicMock, patch, side_effect, assert patterns.

When to use: Testing external dependencies, isolating units, verifying interactions Covers: unittest.mock, pytest-mock, mocking strategies, anti-patterns Key Topics: Mock vs stub vs spy, patching strategies, assertion methods

coverage-guide.md

Coverage analysis and interpretation - tools, metrics, thresholds, CI integration.

When to use: Measuring test effectiveness, finding gaps, enforcing quality gates Covers: coverage.py, pytest-cov, branch coverage, HTML reports, exclusions Key Topics: 80% line coverage target, critical path coverage, differential coverage

python-specific-testing.md

Python-specific testing patterns - async/await, decorators, generators, context managers, type hints.

When to use: Testing Python-specific features Covers: pytest-asyncio, testing decorators, generator testing, mypy integration Key Topics: Async testing, decorator verification, StopIteration, type checking

Quick Reference

pytest vs unittest

Feature	pytest	unittest
Style	Functional	Class-based
Assertions	Plain `assert`	`self.assertEqual()`
Setup	Fixtures	`setUp()/tearDown()`
Discovery	Automatic	`unittest.main()`
Dependencies	pip install pytest	Standard library

Test Organization

project/
├── app/
│   └── module.py
└── tests/
    ├── conftest.py          # Shared fixtures
    ├── test_module.py       # Mirror source structure
    └── integration/
        └── test_api.py

Coverage Goals

Metric	Minimum	Target	Critical Path
Line Coverage	80%	90%+	100%
Branch Coverage	75%	85%+	100%
Function Coverage	85%	90%+	100%

Mocking Decision Matrix

Dependency Type	Strategy	Tool
HTTP API	Stub responses	aioresponses, responses
Database	Test database	pytest fixtures
File I/O	Mock or tmp_path	unittest.mock, pytest
Time/Random	Patch	patch('time.time')
External Service	Mock	unittest.mock.Mock

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