一文带你掌握Python pytest的前后置处理机制与方法

import pytest
@pytest.fixture
def db_connection():
    # 前置：建立连接
    conn = create_connection()
    yield conn
    # 后置：一定会执行（除非 fixture 前置阶段就挂了）
    conn.close()
def test_query(db_connection):
    assert db_connection.query("SELECT 1") == 1

import pytest
@pytest.fixture
def db_connection(request):
    conn = create_connection()
    def cleanup():
        conn.close()
    request.addfinalizer(cleanup)   # 注册后置函数
    return conn

class TestDatabase:
    def setup_method(self):
        self.conn = create_connection()
    def teardown_method(self):
        self.conn.close()   # 每个测试方法结束后一定会执行
    def test_query(self):
        assert self.conn.query("SELECT 1") == 1

@pytest.fixture
def temp_file():
    f = None
    try:
        f = open("/tmp/test.txt", "w")
        yield f
    finally:
        if f:
            f.close()
        # 或者无条件删除文件

def setup_function(function):
    print("\n[前置] 在每个测试函数前执行")
def teardown_function(function):
    print("[后置] 在每个测试函数后执行")
def test_add():
    assert 1 + 1 == 2
def test_multiply():
    assert 2 * 3 == 6

class TestMath:

    def setup_method(self):
        print("\n[前置] 每个测试方法前执行")

    def teardown_method(self):
        print("[后置] 每个测试方法后执行")

    def test_add(self):
        assert 1 + 1 == 2

    def test_multiply(self):
        assert 2 * 3 == 6

class TestDatabase:

    @classmethod
    def setup_class(cls):
        print("\n[前置] 整个测试类只执行一次")

    @classmethod
    def teardown_class(cls):
        print("[后置] 整个测试类只执行一次")

    def test_connection(self):
        assert True

    def test_query(self):
        assert True

# test_example.py
def setup_module(module):
    print("\n[前置] 模块级别，执行一次")

def teardown_module(module):
    print("[后置] 模块级别，执行一次")

def test_a():
    assert True

def test_b():
    assert True

import pytest

@pytest.fixture
def db_connection():
    print("\n[前置] 建立数据库连接")
    conn = {"host": "localhost", "port": 3306}
    yield conn   # 将资源传递给测试函数
    print("[后置] 关闭数据库连接")

def test_query(db_connection):
    assert db_connection["port"] == 3306

@pytest.fixture(scope="module")
def shared_resource():
    print("\n[前置] 模块级别共享资源")
    yield {"data": "shared"}
    print("[后置] 清理共享资源")

@pytest.fixture(autouse=True)
def auto_log():
    print("\n[自动前置] 记录测试开始")
    yield
    print("[自动后置] 记录测试结束")

def test_something():
    assert True   # 前后置会自动执行

@pytest.fixture
def resource(request):
    print(f"测试函数名: {request.node.name}")
    # 可访问 module, cls, function 等
    yield
    print("清理")

import pytest

pytestmark = pytest.mark.usefixtures("db_connection")

def test_1():
    pass

def test_2():
    pass

# conftest.py
import pytest

@pytest.fixture(scope="session")
def global_config():
    return {"env": "test"}

# test_foo.py
def test_config(global_config):
    assert global_config["env"] == "test"