Python pytest 模式

现代 pytest 模式，用于高效测试。

基本测试结构

import pytest

def test_basic():
    """Simple assertion test."""
    assert 1 + 1 == 2

def test_with_description():
    """Descriptive name and docstring."""
    result = calculate_total([1, 2, 3])
    assert result == 6, "Sum should equal 6"

Fixtures

import pytest

@pytest.fixture
def sample_user():
    """Create test user."""
    return {"id": 1, "name": "Test User"}

@pytest.fixture
def db_connection():
    """Fixture with setup and teardown."""
    conn = create_connection()
    yield conn
    conn.close()

def test_user(sample_user):
    """Fixtures injected by name."""
    assert sample_user["name"] == "Test User"

Fixture 作用域

@pytest.fixture(scope="function")  # 默认 - 每个测试
@pytest.fixture(scope="class")     # 每个测试类
@pytest.fixture(scope="module")    # 每个测试文件
@pytest.fixture(scope="session")   # 整个测试运行

参数化

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

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

异常测试

def test_raises():
    with pytest.raises(ValueError) as exc_info:
        raise ValueError("Invalid input")
    assert "Invalid" in str(exc_info.value)

def test_raises_match():
    with pytest.raises(ValueError, match=r".*[Ii]nvalid.*"):
        raise ValueError("Invalid input")

标记

@pytest.mark.skip(reason="Not implemented yet")
def test_future_feature():
    pass

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

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

@pytest.mark.slow
def test_performance():
    """Custom marker - register in pytest.ini."""
    pass

Mock

from unittest.mock import Mock, patch, MagicMock

def test_with_mock():
    mock_api = Mock()
    mock_api.get.return_value = {"status": "ok"}
    result = mock_api.get("/endpoint")
    assert result["status"] == "ok"

@patch("module.external_api")
def test_with_patch(mock_api):
    mock_api.return_value = {"data": []}
    result = function_using_api()
    mock_api.assert_called_once()

pytest-mock（推荐）

def test_with_mocker(mocker):
    mock_api = mocker.patch("module.api_call")
    mock_api.return_value = {"success": True}
    result = process_data()
    assert result["success"]

conftest.py

# tests/conftest.py - 共享 fixtures

import pytest

@pytest.fixture(scope="session")
def app():
    """Application fixture available to all tests."""
    return create_app(testing=True)

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

快速参考

在项目环境中运行 — 前缀 uv run（如 uv run pytest -v）。

| 命令 | 描述 | |------|------| | pytest | 运行所有测试 | | pytest -v | 详细输出 | | pytest -x | 首次失败时停止 | | pytest -k "test_name" | 运行匹配的测试 | | pytest -m slow | 运行标记的测试 | | pytest --lf | 重新运行上次失败的 | | pytest --cov=src | 覆盖率报告 | | pytest -n auto | 并行（pytest-xdist） |

知识参考

pytest 7.0+、Python 3.9+、pytest-asyncio、pytest-mock、pytest-cov、pytest-xdist、conftest、fixtures、参数化、标记