pytest-skill
Generates production-grade pytest tests in Python with fixtures, parametrize, markers, mocking, and conftest patterns. Use when user mentions "pytest", "conftest", "@pytest.fixture", "@pytest.mark", "Python test". Triggers on: "pytest", "conftest", "Python test", "parametrize", "Python unit test".
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/lambdatest/agent-skills --skill pytest-skill- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads pytest-skill automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Pytest Testing Skill
Core Patterns
Basic Test
import pytest
def test_addition():
assert 2 + 3 == 5
def test_exception():
with pytest.raises(ValueError, match="invalid"):
int("not_a_number")
class TestCalculator:
def test_add(self):
calc = Calculator()
assert calc.add(2, 3) == 5
def test_divide_by_zero(self):
with pytest.raises(ZeroDivisionError):
Calculator().divide(10, 0)
Fixtures
@pytest.fixture
def calculator():
return Calculator()
@pytest.fixture
def db_connection():
conn = Database.connect("test_db")
yield conn # teardown after yield
conn.rollback()
conn.close()
@pytest.fixture(scope="module")
def api_client():
client = APIClient(base_url="http://localhost:8000")
yield client
client.logout()
# conftest.py - shared fixtures
@pytest.fixture(autouse=True)
def reset_state():
State.reset()
yield
State.cleanup()
# Usage
def test_add(calculator):
assert calculator.add(2, 3) == 5
Parametrize
@pytest.mark.parametrize("input,expected", [
("hello", 5), ("", 0), ("pytest", 6),
])
def test_string_length(input, expected):
assert len(input) == expected
@pytest.mark.parametrize("a,b,expected", [
(2, 3, 5), (-1, 1, 0), (0, 0, 0),
])
def test_add(calculator, a, b, expected):
assert calculator.add(a, b) == expected
Markers
@pytest.mark.slow
def test_large_dataset(): ...
@pytest.mark.skip(reason="Not implemented")
def test_future_feature(): ...
@pytest.mark.skipif(sys.platform == "win32", reason="Unix only")
def test_unix_permissions(): ...
@pytest.mark.xfail(reason="Known bug #123")
def test_known_bug(): ...
Mocking
from unittest.mock import patch, MagicMock
def test_send_email(mocker):
mock_smtp = mocker.patch("myapp.email.smtplib.SMTP")
send_welcome_email("user@test.com")
mock_smtp.return_value.sendmail.assert_called_once()
def test_api_call(mocker):
mock_response = mocker.Mock()
mock_response.status_code = 200
mock_response.json.return_value = {"users": [{"name": "Alice"}]}
mocker.patch("myapp.service.requests.get", return_value=mock_response)
users = get_users()
assert len(users) == 1
@patch("myapp.service.database")
def test_save_user(mock_db):
mock_db.save.return_value = True
assert save_user({"name": "Alice"}) is True
mock_db.save.assert_called_once()
Assertions
assert x == y
assert x != y
assert x in collection
assert isinstance(obj, MyClass)
assert 0.1 + 0.2 == pytest.approx(0.3)
with pytest.raises(ValueError) as exc_info:
raise ValueError("bad")
assert "bad" in str(exc_info.value)
Anti-Patterns
| Bad | Good | Why |
|---|---|---|
self.assertEqual() | assert x == y | pytest rewrites give better output |
Setup in __init__ | @pytest.fixture | Lifecycle management |
| Global state | Fixture with yield | Proper cleanup |
| Huge test functions | Small focused tests | Easier debugging |
Quick Reference
| Task | Command |
|---|---|
| Run all | pytest |
| Run file | pytest tests/test_login.py |
| Run specific | pytest tests/test_login.py::test_login_success |
| By marker | pytest -m slow |
| By keyword | pytest -k "login and not invalid" |
| Verbose | pytest -v |
| Stop first fail | pytest -x |
| Last failed | pytest --lf |
| Coverage | pytest --cov=myapp --cov-report=html |
| Parallel | pytest -n auto (pytest-xdist) |
pyproject.toml
[tool.pytest.ini_options]
testpaths = ["tests"]
markers = ["slow: slow tests", "integration: integration tests"]
addopts = "-v --tb=short"
Deep Patterns
For production-grade patterns, see reference/playbook.md:
| Section | What's Inside |
|---|---|
| §1 Config | pytest.ini + pyproject.toml with markers, coverage |
| §2 Fixtures | Scoping, factories, teardown, autouse, tmp_path |
| §3 Parametrize | Basic, with IDs, cartesian, indirect |
| §4 Mocking | pytest-mock, monkeypatch, spies, env vars |
| §5 Async | pytest-asyncio, async fixtures, async client |
| §6 Exceptions | pytest.raises(match=), warnings |
| §7 Markers & Plugins | Custom markers, collection hooks |
| §8 Class-Based | Nested classes, autouse setup |
| §9 CI/CD | GitHub Actions matrix, coverage gates |
| §10 Debugging Table | 10 common problems with fixes |
| §11 Best Practices | 15-item production checklist |
FAQ
What does the pytest-skill skill do?
Generates production-grade pytest tests in Python with fixtures, parametrize, markers, mocking, and conftest patterns. Use when user mentions "pytest", "conftest", "@pytest.fixture", "@pytest.mark", "Python test". Triggers on: "pytest", "conftest", "Python test", "parametrize", "Python unit test".
How do I install pytest-skill?
Run npx skills add https://github.com/lambdatest/agent-skills --skill pytest-skill in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/pytest-skill/ (personal) or .claude/skills/pytest-skill/ (project).
Which AI agents can use pytest-skill?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is pytest-skill safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains pytest-skill?
It is published by lambdatest in lambdatest/agent-skills. It has 416 recorded installs.
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