带有笑话的模拟函数，其中包含一个回调作为参数，该函数返回一个promise [英] Mock function with jest that contains a callback as an argument which returns a promise

问题描述

我正在与第三方脚本集成，并且遇到了一个我不知道如何正确测试的场景.

I'm integrating with a 3rd party script and have come across a scenario which I don't know how to test properly.

第三方脚本通过一些方法将对象添加到窗口. create方法的第二个参数是一个回调函数，该函数返回被拒绝或解决的Promise.

The 3rd party script adds an object to the window with a few methods. The second argument of the create method is a callback function which returns a promise that is either rejected or resolved.

我需要能够以拒绝状态或已解决状态来模拟第二个参数，以便我的单元测试可以涵盖是否用错误或成功消息来更新UI.

I need to be able to mock that second argument with either a reject or resolved status so that my unit test can cover whether the UI is updated with either the error or success message.

如何模拟具有适当响应的此函数和回调函数?

How can I mock this function and the callback function with the proper response?

thirdpartyform.create(options, (err, message) => {
  return new Promise((resolve, reject) => {
    if (err) {
      reject(err.reason)
    } else {
      resolve(message)
    }
  })
  .then(message => {
    setState(message)
  })
  .catch((err) => {
    setState(err)
  })
})

以下是我当前尝试模拟不起作用的功能(针对window对象)的尝试.它没有正确设置拒绝值或解析值:(

Below is my current attempt at mocking the function (against the window object) which is not working. It does not properly set the rejected value or resolved value :(

create: jest.fn((options, callback) => callback(jest.fn().mockRejectedValue(FORM_TIMEOUT)))

任何帮助将不胜感激

推荐答案

create是基于回调的，并且不了解promise，因此模拟也不应该包含promise.

create is callback-based and is unaware of promises, so a mock shouldn't involve promises either.

鉴于thirdpartyform.create是先前使用jest.mock，jest.spyOn等设置的间谍，是成功响应的模拟:

Given that thirdpartyform.create is a spy that has been previously set up with jest.mock, jest.spyOn, etc, a mock for successful response:

thirdpartyform.create.mockImplementation((options, cb) => cb(null, 'message'))

响应失败的模拟:

thirdpartyform.create.mockImplementation((options, cb) => cb({ reason: 'error' }))

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