pytest                           # Run all tests
pytest test_mod.py               # Single module
pytest tests/                    # Directory
pytest -k "name"                 # By keyword
pytest -m slow                   # By marker
pytest test_mod.py::test_func    # Specific test
pytest --durations=10            # Show slowest tests

import pytest

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

def test_example(sample_data):
    assert sample_data["key"] == "value"

@pytest.fixture(scope="function")  # Default: per test
@pytest.fixture(scope="class")     # Per test class
@pytest.fixture(scope="module")    # Per module
@pytest.fixture(scope="session")   # Entire session

@pytest.fixture
def db_connection():
    conn = create_connection()
    yield conn
    conn.close()  # Cleanup after test

@pytest.fixture
def make_user():
    def _make_user(name, role="user"):
        return {"name": name, "role": role}
    return _make_user

def test_users(make_user):
    admin = make_user("Alice", role="admin")
    user = make_user("Bob")

@pytest.fixture(params=["mysql", "postgres", "sqlite"])
def database(request):
    return create_db(request.param)

@pytest.mark.parametrize("input,expected", [
    (1, 2),
    (2, 4),
    (3, 6),
])
def test_double(input, expected):
    assert input * 2 == expected

@pytest.mark.parametrize("x", [1, 2])
@pytest.mark.parametrize("y", [10, 20])
def test_multiply(x, y):  # Runs 4 combinations
    assert x * y > 0

@pytest.mark.parametrize("input,expected", [
    (1, 1),
    pytest.param(0, 1, marks=pytest.mark.xfail),
])
def test_factorial(input, expected):
    assert factorial(input) == expected

@pytest.mark.skip(reason="Not implemented")
def test_feature(): ...

@pytest.mark.skipif(sys.platform == "win32", reason="Unix only")
def test_unix(): ...

@pytest.mark.xfail(reason="Known bug")
def test_buggy(): ...

[pytest]
markers =
    slow: marks tests as slow
    integration: integration tests

@pytest.mark.slow
def test_slow_operation(): ...

assert value == expected
assert value != other
assert value is None
assert value is not None
assert value in collection
assert isinstance(obj, MyClass)

assert 0.1 + 0.2 == pytest.approx(0.3)
assert result == pytest.approx(expected, rel=1e-3)

def test_raises():
    with pytest.raises(ValueError):
        int("invalid")

def test_raises_with_match():
    with pytest.raises(ValueError, match=r"invalid.*"):
        raise ValueError("invalid input")

def test_raises_inspect():
    with pytest.raises(ValueError) as exc_info:
        raise ValueError("test error")
    assert "test" in str(exc_info.value)

def test_api_call(monkeypatch):
    def mock_get(*args, **kwargs):
        return {"status": "ok"}

    monkeypatch.setattr("mymodule.api.get", mock_get)
    result = mymodule.fetch_data()
    assert result["status"] == "ok"

def test_with_env(monkeypatch):
    monkeypatch.setenv("API_KEY", "test-key")
    assert os.environ["API_KEY"] == "test-key"

def test_without_env(monkeypatch):
    monkeypatch.delenv("API_KEY", raising=False)

def test_config(monkeypatch):
    monkeypatch.setitem(app.config, "DEBUG", True)

def test_output(capsys):
    print("hello")
    captured = capsys.readouterr()
    assert captured.out == "hello\n"

def test_logging(caplog):
    import logging
    logging.warning("test warning")
    assert "test warning" in caplog.text

def test_temp_file(tmp_path):
    file = tmp_path / "test.txt"
    file.write_text("content")
    assert file.read_text() == "content"

project/
├── pyproject.toml
├── src/
│   └── mypackage/
│       ├── __init__.py
│       └── module.py
└── tests/
    ├── conftest.py      # Shared fixtures
    ├── test_module.py
    └── unit/
        └── test_specific.py

# tests/conftest.py
import pytest

@pytest.fixture
def app():
    return create_app(testing=True)

@pytest.fixture
def client(app):
    return app.test_client()

[tool.pytest.ini_options]
testpaths = ["tests"]
python_files = ["test_*.py"]
python_functions = ["test_*"]
addopts = "-v --strict-markers"
markers = [
    "slow: marks tests as slow",
    "integration: integration tests",
]
filterwarnings = [
    "ignore::DeprecationWarning",
]