Тестирование Python: pytest + fixtures

1# test_calculator.py
2def add(a, b):
3    return a + b
4
5def test_add_positive():
6    assert add(2, 3) == 5
7
8def test_add_negative():
9    assert add(-1, -1) == -2
10
11def test_add_zero():
12    assert add(0, 0) == 0

1class TestCalculator:
2    def test_add(self):
3        assert add(2, 3) == 5
4
5    def test_multiply(self):
6        assert multiply(2, 3) == 6
7
8    def test_divide(self):
9        assert divide(6, 3) == 2
10
11    def test_divide_by_zero(self):
12        with pytest.raises(ZeroDivisionError):
13            divide(1, 0)

1# Все тесты
2pytest
3
4# Конкретный файл
5pytest test_calculator.py
6
7# Конкретный тест
8pytest test_calculator.py::test_add
9
10# С отладкой
11pytest -s
12
13# С подробным выводом
14pytest -v
15
16# Только упавшие
17pytest --tb=short

1import pytest
2
3@pytest.fixture
4def sample_data():
5    return {
6        "users": [
7            {"id": 1, "name": "Alice", "email": "alice@test.com"},
8            {"id": 2, "name": "Bob", "email": "bob@test.com"}
9        ]
10    }
11
12def test_get_user(sample_data):
13    user = sample_data["users"][0]
14    assert user["name"] == "Alice"

1@pytest.fixture(params=["sqlite", "postgresql"])
2def database(request):
3    if request.param == "sqlite":
4        db = create_sqlite_db()
5    else:
6        db = create_postgresql_db()
7
8    yield db
9
10    db.cleanup()
11
12def test_query(database):
13    result = database.query("SELECT * FROM users")
14    assert len(result) > 0

1@pytest.fixture(autouse=True)
2def setup_logging():
3    logging.basicConfig(level=logging.DEBUG)
4    yield
5    logging.shutdown()
6
7# Этот fixture будет применяться ко ВСЕМ тестам в модуле

1@pytest.fixture(scope="session")
2def browser():
3    # Создаётся один раз на всю сессию тестов
4    driver = webdriver.Chrome()
5    yield driver
6    driver.quit()
7
8@pytest.fixture(scope="module")
9def db_connection():
10    # Создаётся один раз на модуль
11    conn = create_connection()
12    yield conn
13    conn.close()
14
15@pytest.fixture(scope="function")
16def clean_db(db_connection):
17    # Создаётся для каждой функции
18    db_connection.execute("DELETE FROM users")
19    yield
20    db_connection.execute("DELETE FROM users")

1@pytest.mark.parametrize("input,expected", [
2    (1, 2),
3    (2, 4),
4    (3, 6),
5    (0, 0),
6    (-1, -2),
7])
8def test_double(input, expected):
9    assert double(input) == expected
10
11# Параметризация с именами
12@pytest.mark.parametrize("user", [
13    pytest.param({"name": "Alice", "role": "admin"}, id="admin"),
14    pytest.param({"name": "Bob", "role": "user"}, id="regular_user"),
15])
16def test_user_role(user):
17    assert user["role"] in ["admin", "user", "moderator"]

1from unittest.mock import patch, MagicMock, AsyncMock
2
3# Мокирование функции
4@patch('myapp.services.external_api.call')
5def test_with_mock(mock_call):
6    mock_call.return_value = {"status": "ok"}
7    result = my_function()
8    assert result == "success"
9    mock_call.assert_called_once()
10
11# Мокирование класса
12def test_with_class_mock():
13    with patch('myapp.db.Database') as MockDB:
14        mock_db = MockDB.return_value
15        mock_db.query.return_value = [{"id": 1}]
16        result = get_users()
17        assert len(result) == 1

1def test_with_mocker(mocker):
2    # mocker — встроенный fixture из pytest-mock
3    mock_func = mocker.patch('myapp.utils.external_call')
4    mock_func.return_value = "mocked"
5
6    result = my_function()
7    assert result == "mocked"
8    mock_func.assert_called_once()

1import pytest
2from unittest.mock import AsyncMock
3
4@pytest.mark.asyncio
5async def test_async_function():
6    mock_db = AsyncMock()
7    mock_db.fetch_user.return_value = {"id": 1, "name": "Alice"}
8
9    result = await get_user_async(1)
10
11    assert result["name"] == "Alice"
12    mock_db.fetch_user.assert_called_once_with(1)

1def test_division_by_zero():
2    with pytest.raises(ZeroDivisionError, match="division by zero"):
3        divide(1, 0)
4
5def test_custom_exception():
6    with pytest.raises(ValueError) as exc_info:
7        validate_email("invalid-email")
8
9    assert "Invalid email" in str(exc_info.value)

1pytest --cov=myapp --cov-report=html

1pytest -n auto  # Использовать все ядра CPU

1@pytest.mark.django_db
2def test_user_creation():
3    user = User.objects.create(name="Test", email="test@test.com")
4    assert user.pk is not None

1tests/
2├── unit/
3│   ├── test_calculator.py
4│   └── test_validator.py
5├── integration/
6│   ├── test_database.py
7│   └── test_api.py
8├── conftest.py  # Общие fixtures
9└── fixtures/
10    └── data.json

1# Плохо
2def test_function(): pass
3
4# Хорошо
5def test_add_returns_sum_of_two_numbers(): pass
6def test_divide_raises_error_on_zero_divisor(): pass
7def test_user_creation_with_valid_data_succeeds(): pass