Pytest Test Creator

Pytest Test Creator Skill

Auto-generate comprehensive unit tests for Python codebases, run tests with pytest, and generate coverage reports using uv for package management.

Workflow

Step 1: Analyze Codebase

1. Find Python files with Glob tool
2. Read source code to identify functions, classes, type signatures, docstrings
3. Check for existing tests to avoid duplication

Step 2: Generate Tests

For each module, create tests/test_<module_name>.py covering:

• Happy path: Normal expected usage
• Edge cases: Boundary conditions, empty inputs
• Error cases: Invalid inputs, exceptions
• Integration: How components work together

Use fixtures for sample data, mock objects, and shared setup.

Step 3: Setup Test Environment

Ensure dependencies are in pyproject.toml:

[project.optional-dependencies]
test = [
    "pytest>=7.4.0",
    "pytest-cov>=4.1.0",
    "pytest-mock>=3.11.0",
]

uv add --dev pytest pytest-cov pytest-mock

Step 4: Run Tests

uv run pytest --cov=src --cov-report=html --cov-report=term-missing

Configuration (pyproject.toml)

[tool.pytest.ini_options]
testpaths = ["tests"]
python_files = ["test_*.py"]
python_classes = ["Test*"]
python_functions = ["test_*"]
addopts = ["--strict-markers", "--strict-config", "-ra"]

[tool.coverage.run]
source = ["src"]
omit = ["*/tests/*", "*/__pycache__/*"]

[tool.coverage.report]
precision = 2
show_missing = true
skip_covered = false

Best Practices

• Naming: test_function_name_with_valid_input(), not test_1()
• Organization: One test file per source module, group related tests in classes
• Coverage: Aim for >80%, focus on critical business logic first
• Independence: No shared mutable state between tests
• What to test: Business logic, data transformations, error handling, edge cases
• What to skip: Third-party library internals, auto-generated code, trivial getters/setters

Scripts

• scripts/generate_tests.py - Analyzes source files and generates test templates with fixtures and parametrize decorators
• scripts/run_tests.py - Runs pytest with coverage and generates reports (--coverage, --html flags)

References

• references/pytest-patterns.md - Comprehensive pytest patterns and examples
• references/mocking-guide.md - Guide to mocking with pytest-mock
• references/coverage-config.md - Coverage configuration and best practices
• references/uv-commands.md - UV package management commands
• references/databricks-notebook-testing.md - Testing Databricks Python notebooks