TDD-Pytest Skill

Activate this skill when the user needs help with:

• Writing tests using TDD methodology (Red-Green-Refactor)

• Auditing existing pytest test files for quality

• Running tests with coverage

• Generating test reports to TESTING_REPORT.local.md

• Setting up pytest configuration in pyproject.toml

TDD Workflow

Red-Green-Refactor Cycle

RED - Write a failing test first

• Test should fail for the right reason (not import errors)

• Test should be minimal and focused

• Show the failing test output

GREEN - Write minimal code to pass

• Only implement what's needed to pass the test

• No premature optimization

• Show the passing test output

REFACTOR - Improve code while keeping tests green

• Clean up duplication

• Improve naming

• Extract functions/classes if needed

• Run tests after each change

Test Organization

File Structure

project/ src/ module.py tests/ conftest.py # Shared fixtures test_module.py # Tests for module.py pyproject.toml # Pytest configuration

Naming Conventions

• Test files: test_*.py or *_test.py

• Test functions: test_*

• Test classes: Test*

• Fixtures: Descriptive names (mock_database , sample_user )

Pytest Best Practices

Fixtures

import pytest

@pytest.fixture def sample_config(): return {"key": "value"}

@pytest.fixture def mock_client(mocker): return mocker.MagicMock()

Parametrization

@pytest.mark.parametrize("input,expected", [ ("hello", "HELLO"), ("world", "WORLD"), ("", ""), ]) def test_uppercase(input, expected): assert input.upper() == expected

Async Tests

import pytest

@pytest.mark.asyncio async def test_async_function(): result = await async_operation() assert result == expected

Exception Testing

def test_raises_value_error(): with pytest.raises(ValueError, match="invalid input"): process_input(None)

Running Tests

With uv

uv run pytest # Run all tests uv run pytest tests/test_module.py # Run specific file uv run pytest -k "test_name" # Run by name pattern uv run pytest -v --tb=short # Verbose with short traceback uv run pytest --cov=src --cov-report=term # With coverage

Common Flags

• -v / --verbose

• Detailed output

• -x / --exitfirst

• Stop on first failure

• --tb=short

• Short tracebacks

• --tb=no

• No tracebacks

• -k EXPR

• Run tests matching expression

• -m MARKER

• Run tests with marker

• --cov=PATH

• Coverage for path

• --cov-report=term-missing

• Show missing lines

pyproject.toml Configuration

Minimal Setup

[tool.pytest.ini_options] asyncio_mode = "auto" testpaths = ["tests"]

Full Configuration

[tool.pytest.ini_options] asyncio_mode = "auto" asyncio_default_fixture_loop_scope = "function" testpaths = ["tests"] python_files = ["test_.py", "test.py"] python_functions = ["test"] python_classes = ["Test"] addopts = "-v --tb=short" markers = [ "slow: marks tests as slow", "integration: marks integration tests", ] filterwarnings = [ "ignore::DeprecationWarning", ]

[tool.coverage.run] source = ["src"] branch = true omit = ["tests/", "/init.py"]

[tool.coverage.report] exclude_lines = [ "pragma: no cover", "if TYPE_CHECKING:", "raise NotImplementedError", ] fail_under = 80 show_missing = true

Report Generation

The TESTING_REPORT.local.md file should contain:

• Test execution summary (passed/failed/skipped)

• Coverage metrics by module

• Audit findings by severity

• Recommendations with file:line references

• Evidence (command outputs)

Integration with Conversation

When the user asks to write tests:

• Check conversation history for context about what to test

• Identify the code/feature being discussed

• If unclear, ask clarifying questions:

• "What specific behavior should I test?"

• "Should I include edge cases for X?"

• "Do you want unit tests, integration tests, or both?"

• Follow TDD: Write failing test first, then implement

Commands Available

• /tdd-pytest:init

• Initialize pytest configuration

• /tdd-pytest:test [path]

• Write tests using TDD (context-aware)

• /tdd-pytest:test-all

• Run all tests

• /tdd-pytest:report

• Generate/update TESTING_REPORT.local.md