如何用玩笑在模拟函数中断言类的属性

Question

我遇到了将类作为参数传递的模拟函数的问题。由于某种原因，它似乎没有正确断言内容

// ErrorHandler.js
class ErrorHandler extends Error {
  constructor(status, reason) {
    super();
    this.status = status;
    this.reason = reason;
  }
}

export {
  ErrorHandler
}

// express file express.js
const method = async (req, res, next) => {
  try {
    throw new ErrorHandler(401, 'error')
    next()
  } catch (error) {
    next(error)
  }
}

// test file
it('should call the next method with the proper error', async () => {
 const request = {
   body: {}
 }
 const next = jest.fn()
 const response = mockResponse() // here it's just a simple mock
 await method(request, response, next)

 expect(next).toHaveBeenCalledWith(
  // here the problem is that it doesn't seem to assert the parameters
  // and this test is passing
  new ErrorHandler('random text')
 )
})

我尝试模拟 ErrorHandler 类，但是它给出了另一个错误，它无法再比较下一个方法

Answer 1

问题在于 Jest 试图比较两个错误对象，但并不真正知道如何进行比较。您可以通过一个简单的断言来看到这一点：

expect(new ErrorHandler(404, 'not found')).not.toEqual(new ErrorHandler(401, 'unauthorized'))

结果：

expect(received).not.toEqual(expected) // deep equality

Expected: not [Error]

你需要更具体，例如：

expect(next).toHaveBeenCalled();
const [err] = next.mock.calls[0];
expect(err).toMatchObject({ status: 401, reason: 'error' });