Agent skill
pytest
Expert guidance for Python testing with pytest framework. Use when (1) writing unit tests or integration tests, (2) setting up test fixtures for setup/teardown, (3) parametrizing tests with multiple inputs, (4) using markers (skip, xfail, custom), (5) mocking/patching with monkeypatch or pytest-mock, (6) configuring pytest (pytest.ini, pyproject.toml, conftest.py), (7) running tests with coverage, (8) debugging test failures, or (9) testing async code, FastAPI, Django, or Flask apps.
Stars
163
Forks
31
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/pytest-salmanferozkhan-cloud-and-fast-api
SKILL.md
Pytest Testing Guide
Write Python tests efficiently with pytest.
Quick Start
bash
pip install pytest
python
# test_example.py
def test_addition():
assert 1 + 1 == 2
Run: pytest or pytest -v
Core Concepts
| Concept | Example |
|---|---|
| Test function | def test_something(): |
| Assertion | assert result == expected |
| Fixture | @pytest.fixture - dependency injection |
| Marker | @pytest.mark.skip - test metadata |
| Parametrize | @pytest.mark.parametrize - multiple inputs |
Essential Patterns
Basic Test
python
def test_function():
result = my_function(1, 2)
assert result == 3
Exception Testing
python
import pytest
def test_raises():
with pytest.raises(ValueError, match="invalid"):
raise ValueError("invalid input")
Fixture (Setup/Teardown)
python
@pytest.fixture
def database():
db = create_db()
yield db # provide to test
db.cleanup() # teardown
def test_query(database):
assert database.query("SELECT 1")
Parametrize
python
@pytest.mark.parametrize("input,expected", [
(1, 2),
(2, 4),
(3, 6),
])
def test_double(input, expected):
assert input * 2 == expected
Mocking
python
def test_mock(monkeypatch):
monkeypatch.setattr("module.func", lambda: "mocked")
monkeypatch.setenv("API_KEY", "test-key")
Reference Files
| Topic | File | When to Use |
|---|---|---|
| Basics | basics.md | Test discovery, assertions, running tests, config |
| Fixtures | fixtures.md | Setup/teardown, scopes, factories, conftest.py |
| Markers | markers.md | skip, xfail, parametrize, custom markers |
| Mocking | mocking.md | monkeypatch, pytest-mock, spies, async mocks |
| Plugins | plugins.md | Coverage, parallel, async, Django, Flask, FastAPI |
Common Commands
bash
pytest # Run all tests
pytest -v # Verbose
pytest -s # Show prints
pytest -x # Stop on first failure
pytest -k "pattern" # Run matching tests
pytest -m slow # Run by marker
pytest --cov=mypackage # With coverage
pytest -n auto # Parallel (xdist)
pytest --lf # Run last failed
pytest --pdb # Debug on failure
Project Structure
project/
├── src/
│ └── mypackage/
│ └── module.py
├── tests/
│ ├── conftest.py # Shared fixtures
│ ├── test_unit.py
│ └── test_integration.py
├── pytest.ini # Or pyproject.toml
└── requirements-test.txt
Configuration (pyproject.toml)
toml
[tool.pytest.ini_options]
testpaths = ["tests"]
addopts = "-v --tb=short"
markers = [
"slow: slow tests",
"integration: integration tests",
]
Built-in Fixtures
| Fixture | Purpose |
|---|---|
tmp_path |
Temp directory (pathlib.Path) |
tmpdir |
Temp directory (legacy) |
capsys |
Capture stdout/stderr |
caplog |
Capture logging |
monkeypatch |
Patch attributes/env vars |
request |
Test/fixture metadata |
Fixture Scopes
python
@pytest.fixture(scope="function") # Default - per test
@pytest.fixture(scope="class") # Per test class
@pytest.fixture(scope="module") # Per file
@pytest.fixture(scope="session") # Per test run
Best Practices
- Name tests descriptively:
test_user_login_with_invalid_password_fails - One assertion concept per test
- Use fixtures for reusable setup
- Use
conftest.pyfor shared fixtures - Use markers to categorize tests (unit, integration, slow)
- Run with coverage:
pytest --cov --cov-report=html - Use parametrize to reduce duplicate tests
Didn't find tool you were looking for?