如何使用mocking/patching更改类方法中的本地目录变量，以避免将测试输出文件写入其中？

import os
from unittest.mock import patch

class MyClass:
    def write_to_file(self, data):
        # 将数据写入本地目录变量指定的目录
        file_path = os.path.join(self.local_directory, 'output.txt')
        with open(file_path, 'w') as f:
            f.write(data)

# 测试代码
def test_write_to_file():
    # 创建一个Mock对象来替代MyClass类的实例
    mock_obj = MyClass()

    # 使用patch装饰器来修改类方法中的本地目录变量
    with patch.object(mock_obj, 'local_directory', '/tmp'):
        data = 'test data'
        mock_obj.write_to_file(data)

        # 验证文件是否被写入指定目录
        file_path = os.path.join('/tmp', 'output.txt')
        assert os.path.exists(file_path)
        with open(file_path, 'r') as f:
            assert f.read() == data

# 运行测试
test_write_to_file()