Python Testing

affaan-m/ECC/docs/ja-JP/skills/python-testing

by affaan-mef648e01899ba3e8dc6371642deaaf64b4477775No license275K starsListed Oct 9, 2026Updated Oct 9, 2026Repository updated 4 days ago

pytest、TDD手法、フィクスチャ、モック、パラメータ化、カバレッジ要件を使用したPythonテスト戦略。

Instructions onlySoftware Development
AI-generated overview

Guides Python testing with pytest, TDD, fixtures, mocking, parametrization and coverage targets.

What it does
This skill provides reference guidance for writing and organizing Python tests with pytest. It covers the TDD red-green-refactor cycle, assertions, fixtures and their scopes, parametrization, markers, mocking and patching, async tests, exception testing, temporary file handling, and test directory layout. It also gives pytest.ini and pyproject.toml configuration examples, common command-line invocations, and coverage goals such as 80 percent overall and 100 percent on critical paths.
When to use it
Use it when writing new Python code under TDD, designing a project's test suite, reviewing Python test coverage, or setting up test infrastructure. It is aimed at pytest-based Python projects.
Requirements
Requires pytest; examples also reference pytest-cov for coverage, pytest-asyncio for async tests, and unittest.mock from the standard library. It ships no scripts and is instructions only.

Pythonテストパターン

pytest、TDD方法論、ベストプラクティスを使用したPythonアプリケーションの包括的なテスト戦略。

いつ有効化するか

  • 新しいPythonコードを書くとき（TDDに従う：赤、緑、リファクタリング）
  • Pythonプロジェクトのテストスイートを設計するとき
  • Pythonテストカバレッジをレビューするとき
  • テストインフラストラクチャをセットアップするとき

核となるテスト哲学

テスト駆動開発（TDD）

常にTDDサイクルに従います。

  1. 赤: 期待される動作のための失敗するテストを書く
  2. 緑: テストを通過させるための最小限のコードを書く
  3. リファクタリング: テストを通過させたままコードを改善する
python
# Step 1: Write failing test (RED)def test_add_numbers():    result = add(2, 3)    assert result == 5
# Step 2: Write minimal implementation (GREEN)def add(a, b):    return a + b
# Step 3: Refactor if needed (REFACTOR)

カバレッジ要件

  • 目標: 80%以上のコードカバレッジ
  • クリティカルパス: 100%のカバレッジが必要
  • pytest --covを使用してカバレッジを測定
bash
pytest --cov=mypackage --cov-report=term-missing --cov-report=html

pytestの基礎

基本的なテスト構造

python
import pytest
def test_addition():    """Test basic addition."""    assert 2 + 2 == 4
def test_string_uppercase():    """Test string uppercasing."""    text = "hello"    assert text.upper() == "HELLO"
def test_list_append():    """Test list append."""    items = [1, 2, 3]    items.append(4)    assert 4 in items    assert len(items) == 4

アサーション

python
# Equalityassert result == expected
# Inequalityassert result != unexpected
# Truthinessassert result  # Truthyassert not result  # Falsyassert result is True  # Exactly Trueassert result is False  # Exactly Falseassert result is None  # Exactly None
# Membershipassert item in collectionassert item not in collection
# Comparisonsassert result > 0assert 0 <= result <= 100
# Type checkingassert isinstance(result, str)
# Exception testing (preferred approach)with pytest.raises(ValueError):    raise ValueError("error message")
# Check exception messagewith pytest.raises(ValueError, match="invalid input"):    raise ValueError("invalid input provided")
# Check exception attributeswith pytest.raises(ValueError) as exc_info:    raise ValueError("error message")assert str(exc_info.value) == "error message"

フィクスチャ

基本的なフィクスチャ使用

python
import pytest
@pytest.fixturedef sample_data():    """Fixture providing sample data."""    return {"name": "Alice", "age": 30}
def test_sample_data(sample_data):    """Test using the fixture."""    assert sample_data["name"] == "Alice"    assert sample_data["age"] == 30

セットアップ/ティアダウン付きフィクスチャ

python
@pytest.fixturedef database():    """Fixture with setup and teardown."""    # Setup    db = Database(":memory:")    db.create_tables()    db.insert_test_data()
    yield db  # Provide to test
    # Teardown    db.close()
def test_database_query(database):    """Test database operations."""    result = database.query("SELECT * FROM users")    assert len(result) > 0

フィクスチャスコープ

python
# Function scope (default) - runs for each test@pytest.fixturedef temp_file():    with open("temp.txt", "w") as f:        yield f    os.remove("temp.txt")
# Module scope - runs once per module@pytest.fixture(scope="module")def module_db():    db = Database(":memory:")    db.create_tables()    yield db    db.close()
# Session scope - runs once per test session@pytest.fixture(scope="session")def shared_resource():    resource = ExpensiveResource()    yield resource    resource.cleanup()

パラメータ付きフィクスチャ

python
@pytest.fixture(params=[1, 2, 3])def number(request):    """Parameterized fixture."""    return request.param
def test_numbers(number):    """Test runs 3 times, once for each parameter."""    assert number > 0

複数のフィクスチャ使用

python
@pytest.fixturedef user():    return User(id=1, name="Alice")
@pytest.fixturedef admin():    return User(id=2, name="Admin", role="admin")
def test_user_admin_interaction(user, admin):    """Test using multiple fixtures."""    assert admin.can_manage(user)

自動使用フィクスチャ

python
@pytest.fixture(autouse=True)def reset_config():    """Automatically runs before every test."""    Config.reset()    yield    Config.cleanup()
def test_without_fixture_call():    # reset_config runs automatically    assert Config.get_setting("debug") is False

共有フィクスチャ用のConftest.py

python
# tests/conftest.pyimport pytest
@pytest.fixturedef client():    """Shared fixture for all tests."""    app = create_app(testing=True)    with app.test_client() as client:        yield client
@pytest.fixturedef auth_headers(client):    """Generate auth headers for API testing."""    response = client.post("/api/login", json={        "username": "test",        "password": "test"    })    token = response.json["token"]    return {"Authorization": f"Bearer {token}"}

パラメータ化

基本的なパラメータ化

python
@pytest.mark.parametrize("input,expected", [    ("hello", "HELLO"),    ("world", "WORLD"),    ("PyThOn", "PYTHON"),])def test_uppercase(input, expected):    """Test runs 3 times with different inputs."""    assert input.upper() == expected

複数パラメータ

python
@pytest.mark.parametrize("a,b,expected", [    (2, 3, 5),    (0, 0, 0),    (-1, 1, 0),    (100, 200, 300),])def test_add(a, b, expected):    """Test addition with multiple inputs."""    assert add(a, b) == expected

ID付きパラメータ化

python
@pytest.mark.parametrize("input,expected", [    ("[email protected]", True),    ("invalid", False),    ("@no-domain.com", False),], ids=["valid-email", "missing-at", "missing-domain"])def test_email_validation(input, expected):    """Test email validation with readable test IDs."""    assert is_valid_email(input) is expected

パラメータ化フィクスチャ

python
@pytest.fixture(params=["sqlite", "postgresql", "mysql"])def db(request):    """Test against multiple database backends."""    if request.param == "sqlite":        return Database(":memory:")    elif request.param == "postgresql":        return Database("postgresql://localhost/test")    elif request.param == "mysql":        return Database("mysql://localhost/test")
def test_database_operations(db):    """Test runs 3 times, once for each database."""    result = db.query("SELECT 1")    assert result is not None

マーカーとテスト選択

カスタムマーカー

python
# Mark slow tests@pytest.mark.slowdef test_slow_operation():    time.sleep(5)
# Mark integration tests@pytest.mark.integrationdef test_api_integration():    response = requests.get("https://api.example.com")    assert response.status_code == 200
# Mark unit tests@pytest.mark.unitdef test_unit_logic():    assert calculate(2, 3) == 5

特定のテストを実行

bash
# Run only fast testspytest -m "not slow"
# Run only integration testspytest -m integration
# Run integration or slow testspytest -m "integration or slow"
# Run tests marked as unit but not slowpytest -m "unit and not slow"

pytest.iniでマーカーを設定

ini
[pytest]markers =    slow: marks tests as slow    integration: marks tests as integration tests    unit: marks tests as unit tests    django: marks tests as requiring Django

モックとパッチ

関数のモック

python
from unittest.mock import patch, Mock
@patch("mypackage.external_api_call")def test_with_mock(api_call_mock):    """Test with mocked external API."""    api_call_mock.return_value = {"status": "success"}
    result = my_function()
    api_call_mock.assert_called_once()    assert result["status"] == "success"

戻り値のモック

python
@patch("mypackage.Database.connect")def test_database_connection(connect_mock):    """Test with mocked database connection."""    connect_mock.return_value = MockConnection()
    db = Database()    db.connect()
    connect_mock.assert_called_once_with("localhost")

例外のモック

python
@patch("mypackage.api_call")def test_api_error_handling(api_call_mock):    """Test error handling with mocked exception."""    api_call_mock.side_effect = ConnectionError("Network error")
    with pytest.raises(ConnectionError):        api_call()
    api_call_mock.assert_called_once()

コンテキストマネージャのモック

python
@patch("builtins.open", new_callable=mock_open)def test_file_reading(mock_file):    """Test file reading with mocked open."""    mock_file.return_value.read.return_value = "file content"
    result = read_file("test.txt")
    mock_file.assert_called_once_with("test.txt", "r")    assert result == "file content"

Autospec使用

python
@patch("mypackage.DBConnection", autospec=True)def test_autospec(db_mock):    """Test with autospec to catch API misuse."""    db = db_mock.return_value    db.query("SELECT * FROM users")
    # This would fail if DBConnection doesn't have query method    db_mock.assert_called_once()

クラスインスタンスのモック

python
class TestUserService:    @patch("mypackage.UserRepository")    def test_create_user(self, repo_mock):        """Test user creation with mocked repository."""        repo_mock.return_value.save.return_value = User(id=1, name="Alice")
        service = UserService(repo_mock.return_value)        user = service.create_user(name="Alice")
        assert user.name == "Alice"        repo_mock.return_value.save.assert_called_once()

プロパティのモック

python
@pytest.fixturedef mock_config():    """Create a mock with a property."""    config = Mock()    type(config).debug = PropertyMock(return_value=True)    type(config).api_key = PropertyMock(return_value="test-key")    return config
def test_with_mock_config(mock_config):    """Test with mocked config properties."""    assert mock_config.debug is True    assert mock_config.api_key == "test-key"

非同期コードのテスト

pytest-asyncioを使用した非同期テスト

python
import pytest
@pytest.mark.asyncioasync def test_async_function():    """Test async function."""    result = await async_add(2, 3)    assert result == 5
@pytest.mark.asyncioasync def test_async_with_fixture(async_client):    """Test async with async fixture."""    response = await async_client.get("/api/users")    assert response.status_code == 200

非同期フィクスチャ

python
@pytest.fixtureasync def async_client():    """Async fixture providing async test client."""    app = create_app()    async with app.test_client() as client:        yield client
@pytest.mark.asyncioasync def test_api_endpoint(async_client):    """Test using async fixture."""    response = await async_client.get("/api/data")    assert response.status_code == 200

非同期関数のモック

python
@pytest.mark.asyncio@patch("mypackage.async_api_call")async def test_async_mock(api_call_mock):    """Test async function with mock."""    api_call_mock.return_value = {"status": "ok"}
    result = await my_async_function()
    api_call_mock.assert_awaited_once()    assert result["status"] == "ok"

例外のテスト

期待される例外のテスト

python
def test_divide_by_zero():    """Test that dividing by zero raises ZeroDivisionError."""    with pytest.raises(ZeroDivisionError):        divide(10, 0)
def test_custom_exception():    """Test custom exception with message."""    with pytest.raises(ValueError, match="invalid input"):        validate_input("invalid")

例外属性のテスト

python
def test_exception_with_details():    """Test exception with custom attributes."""    with pytest.raises(CustomError) as exc_info:        raise CustomError("error", code=400)
    assert exc_info.value.code == 400    assert "error" in str(exc_info.value)

副作用のテスト

ファイル操作のテスト

python
import tempfileimport os
def test_file_processing():    """Test file processing with temp file."""    with tempfile.NamedTemporaryFile(mode='w', delete=False, suffix='.txt') as f:        f.write("test content")        temp_path = f.name
    try:        result = process_file(temp_path)        assert result == "processed: test content"    finally:        os.unlink(temp_path)

pytestのtmp_pathフィクスチャを使用したテスト

python
def test_with_tmp_path(tmp_path):    """Test using pytest's built-in temp path fixture."""    test_file = tmp_path / "test.txt"    test_file.write_text("hello world")
    result = process_file(str(test_file))    assert result == "hello world"    # tmp_path automatically cleaned up

tmpdirフィクスチャを使用したテスト

python
def test_with_tmpdir(tmpdir):    """Test using pytest's tmpdir fixture."""    test_file = tmpdir.join("test.txt")    test_file.write("data")
    result = process_file(str(test_file))    assert result == "data"

テストの整理

ディレクトリ構造

tests/├── conftest.py                 # 共有フィクスチャ├── __init__.py├── unit/                       # ユニットテスト│   ├── __init__.py│   ├── test_models.py│   ├── test_utils.py│   └── test_services.py├── integration/                # 統合テスト│   ├── __init__.py│   ├── test_api.py│   └── test_database.py└── e2e/                        # エンドツーエンドテスト    ├── __init__.py    └── test_user_flow.py

テストクラス

python
class TestUserService:    """Group related tests in a class."""
    @pytest.fixture(autouse=True)    def setup(self):        """Setup runs before each test in this class."""        self.service = UserService()
    def test_create_user(self):        """Test user creation."""        user = self.service.create_user("Alice")        assert user.name == "Alice"
    def test_delete_user(self):        """Test user deletion."""        user = User(id=1, name="Bob")        self.service.delete_user(user)        assert not self.service.user_exists(1)

ベストプラクティス

すべきこと

  • TDDに従う: コードの前にテストを書く（赤-緑-リファクタリング）
  • 一つのことをテスト: 各テストは単一の動作を検証すべき
  • 説明的な名前を使用: test_user_login_with_invalid_credentials_fails
  • フィクスチャを使用: フィクスチャで重複を排除
  • 外部依存をモック: 外部サービスに依存しない
  • エッジケースをテスト: 空の入力、None値、境界条件
  • 80%以上のカバレッジを目指す: クリティカルパスに焦点を当てる
  • テストを高速に保つ: マークを使用して遅いテストを分離

してはいけないこと

  • 実装をテストしない: 内部ではなく動作をテスト
  • テストで複雑な条件文を使用しない: テストをシンプルに保つ
  • テスト失敗を無視しない: すべてのテストは通過する必要がある
  • サードパーティコードをテストしない: ライブラリが機能することを信頼
  • テスト間で状態を共有しない: テストは独立すべき
  • テストで例外をキャッチしない: pytest.raisesを使用
  • print文を使用しない: アサーションとpytestの出力を使用
  • 脆弱すぎるテストを書かない: 過度に具体的なモックを避ける

一般的なパターン

APIエンドポイントのテスト（FastAPI/Flask）

python
@pytest.fixturedef client():    app = create_app(testing=True)    return app.test_client()
def test_get_user(client):    response = client.get("/api/users/1")    assert response.status_code == 200    assert response.json["id"] == 1
def test_create_user(client):    response = client.post("/api/users", json={        "name": "Alice",        "email": "[email protected]"    })    assert response.status_code == 201    assert response.json["name"] == "Alice"

データベース操作のテスト

python
@pytest.fixturedef db_session():    """Create a test database session."""    session = Session(bind=engine)    session.begin_nested()    yield session    session.rollback()    session.close()
def test_create_user(db_session):    user = User(name="Alice", email="[email protected]")    db_session.add(user)    db_session.commit()
    retrieved = db_session.query(User).filter_by(name="Alice").first()    assert retrieved.email == "[email protected]"

クラスメソッドのテスト

python
class TestCalculator:    @pytest.fixture    def calculator(self):        return Calculator()
    def test_add(self, calculator):        assert calculator.add(2, 3) == 5
    def test_divide_by_zero(self, calculator):        with pytest.raises(ZeroDivisionError):            calculator.divide(10, 0)

pytest設定

pytest.ini

ini
[pytest]testpaths = testspython_files = test_*.pypython_classes = Test*python_functions = test_*addopts =    --strict-markers    --disable-warnings    --cov=mypackage    --cov-report=term-missing    --cov-report=htmlmarkers =    slow: marks tests as slow    integration: marks tests as integration tests    unit: marks tests as unit tests

pyproject.toml

toml
[tool.pytest.ini_options]testpaths = ["tests"]python_files = ["test_*.py"]python_classes = ["Test*"]python_functions = ["test_*"]addopts = [    "--strict-markers",    "--cov=mypackage",    "--cov-report=term-missing",    "--cov-report=html",]markers = [    "slow: marks tests as slow",    "integration: marks tests as integration tests",    "unit: marks tests as unit tests",]

テストの実行

bash
# Run all testspytest
# Run specific filepytest tests/test_utils.py
# Run specific testpytest tests/test_utils.py::test_function
# Run with verbose outputpytest -v
# Run with coveragepytest --cov=mypackage --cov-report=html
# Run only fast testspytest -m "not slow"
# Run until first failurepytest -x
# Run and stop on N failurespytest --maxfail=3
# Run last failed testspytest --lf
# Run tests with patternpytest -k "test_user"
# Run with debugger on failurepytest --pdb

クイックリファレンス

パターン使用法
pytest.raises()期待される例外をテスト
@pytest.fixture()再利用可能なテストフィクスチャを作成
@pytest.mark.parametrize()複数の入力でテストを実行
@pytest.mark.slow遅いテストをマーク
pytest -m "not slow"遅いテストをスキップ
@patch()関数とクラスをモック
tmp_pathフィクスチャ自動一時ディレクトリ
pytest --covカバレッジレポートを生成
assertシンプルで読みやすいアサーション

覚えておいてください: テストもコードです。それらをクリーンで、読みやすく、保守可能に保ちましょう。良いテストはバグをキャッチし、優れたテストはそれらを防ぎます。

Source and attribution

Source:affaan-m/ECCindocs/ja-JP/skills/python-testingat commitef648e0

License: No license

Content belongs to its original authors. SourceWeft indexes it from a public repository.

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