如何使用单元测试mock.patch模拟两个函数

# 假设这是我们要测试的模块 my_module.py
def function_a():
    # 实际的实现可能会调用外部服务或执行复杂的操作
    return "real result from function_a"

def function_b():
    # 实际的实现可能会调用外部服务或执行复杂的操作
    return "real result from function_b"

def main_function():
    result_a = function_a()
    result_b = function_b()
    return f"{result_a} and {result_b}"

import unittest
from unittest.mock import patch
from my_module import main_function

class TestMainFunction(unittest.TestCase):

    @patch('my_module.function_a')
    @patch('my_module.function_b')
    def test_main_function(self, mock_function_b, mock_function_a):
        # 设置模拟函数的返回值
        mock_function_a.return_value = "mocked result from function_a"
        mock_function_b.return_value = "mocked result from function_b"

        # 调用main_function并断言结果
        result = main_function()
        self.assertEqual(result, "mocked result from function_a and mocked result from function_b")

        # 断言模拟函数被调用
        mock_function_a.assert_called_once()
        mock_function_b.assert_called_once()

if __name__ == '__main__':
    unittest.main()