python - 每次实例化类时，如何模拟 Python 类以返回唯一的 autospec Mock 实例？

Question

我正在编写一个创建subprocess.Popen管道的程序。我正在尝试模拟subprocess.Popen，以便每个调用都返回一个不同的MagicMock，以便我可以确保在管道中的特定（或所有）进程上调用方法。

我也希望这个模拟基于自动规范，subprocess.Popen但不断收到一个错误，我不能基于模拟自动规范。

目前我的代码如下：

@pytest.fixture
def Popen(mocker: 'pytest_mock.MockFixture'):
    def popen_factory(*args, **kwargs):
        popen = mocker.MagicMock()  # mocker.create_autospec(subprocess.Popen)
        popen.stdin = open(os.devnull, "wb")
        popen.stdout = open(os.devnull, "rb")
        popen.wait.return_value = 0
        return popen

    Popen = mocker.patch.object(subprocess, 'Popen', autospec=True)
    Popen.side_effect = popen_factory
    yield Popen

Answer 1

由于mocker.patch.object(subprocess, 'Popen', autospec=True)overwrites subprocess.Popen，我必须将现有值分配给局部变量，然后改用它。

@pytest.fixture
def Popen(mocker: 'pytest_mock.MockFixture'):
    real_Popen = subprocess.Popen

    def popen_factory(*args, **kwargs):
        popen = mocker.create_autospec(real_Popen)
        popen.stdin = open(os.devnull, "wb")
        popen.stdout = open(os.devnull, "rb")
        popen.wait.return_value = 0
        return popen

    Popen = mocker.patch.object(subprocess, 'Popen', autospec=True)
    Popen.side_effect = popen_factory
    yield Popen