补丁不模拟模块

Question

我正在尝试模拟 subprocess.Popen。但是，当我运行以下代码时，模拟完全被忽略了，我不知道为什么

测试代码：

def test_bring_connection_up(self):
    # All settings should either overload the update or the run method
    mock_popen = MagicMock()
    mock_popen.return_value = {'communicate': (lambda: 'hello','world')}
    with patch('subprocess.Popen', mock_popen):
        self.assertEqual(network_manager.bring_connection_up("test"), "Error: Unknown connection: test.\n")

---

模块代码：

from subprocess import Popen, PIPE
# ........
def list_connections():
    process = Popen(["nmcli", "-t", "-fields", "NAME,TYPE", "con", "list"], stdout=PIPE, stderr=PIPE)
    stdout, stderr = process.communicate() # <--- Here's the failure
    return stdout

Answer 1

您没有在正确的位置进行修补。您在定义 Popen 的位置打补丁：

with patch('subprocess.Popen', mock_popen):

您需要修补 Popen 的导入位置，即在您编写此行的“模块代码”中：

from subprocess import Popen, PIPE

也就是说，它应该看起来像：

with patch('myapp.mymodule.Popen', mock_popen):

如需快速指南，请阅读文档中的部分：Where to patch。