如何使用Jest模拟/测试requestjs requestcallback

Question

我使用requestjs向API发出get请求，然后在requestCallBack中将主体映射到自定义的json对象。我试着用Jest测试这段代码，但不管我怎么嘲弄它，它似乎都不起作用

我尝试过request.get.mockImplementation()，这似乎只是在嘲笑get，而不允许我在回调中测试代码

    await request.get('endpoint', requestOptions, (err, res, body) => { transformBodyContent(body) })

    jest.mock('request')
    jest.mock('request-promise-native')

    import request from 'request-promise-native'

    test('test requestCallback code', async () => {
        // not sure how to test that bodyTransformer is called and is working
    }

Answer 1

您可以使用mockFn.mock.calls获得模拟调用的参数。

在本例中，request.get是一个模拟函数(因为整个request-promise-native是自动嘲弄)，所以您可以使用request.get.mock.calls来获取调用它的参数。第三个参数将是您的回调，因此您可以检索它，然后像这样测试它：

jest.mock('request-promise-native');

import request from 'request-promise-native';

test('test requestCallback code', () => {
  request.get('endpoint', requestOptions, (err, res, body) => { transformBodyContent(body) });

  const firstCallArgs = request.get.mock.calls[0];  // get the args the mock was called with
  const callback = firstCallArgs[2];  // callback is the third argument

  // test callback here
});