Question

我正在尝试使用Jest对一个函数进行单元测试，而且我在处理jest模拟模块时遇到了一些麻烦（相当于nodejs世界中的rewire或proxyquire）。

我实际上是在尝试测试已经使用一些参数在模拟模块上调用间谍。这是我要测试的功能。

注意：当前测试仅涉及“fetch（...）”部分，我试图测试已使用good参数调用fetch。

  File "/usr/lib64/python2.7/heapq.py", line 427, in nsmallest
    result = _nsmallest(n, it)
  File "<stdin>", line 1, in <lambda>
TypeError: bad operand type for unary -: 'unicode'

返回的函数充当闭包，因此“捕获”我想要模拟的节点获取外部模块。

这是我试图通过绿色的测试：

export const fetchRemote = slug => {
    return dispatch => {
        dispatch(loading());
        return fetch(Constants.URL + slug)
            .then(res => res.json())
            .then(cmp => {
                if (cmp.length === 1) {
                    return dispatch(setCurrent(cmp[0]));
                }
                return dispatch(computeRemote(cmp));
            });
    };
};

编辑：第一个答案对编写测试有很大帮助，我现在有以下一个：

it('should have called the fetch function wih the good const parameter and slug', done => {
            const slug = 'slug';
            const spy = jasmine.createSpy();
            const stubDispatch = () => Promise.resolve({json: () => []});
            jest.mock('node-fetch', () => spy);
            const dispatcher = fetchRemote(slug);
            dispatcher(stubDispatch).then(() => {
                expect(spy).toHaveBeenCalledWith(Constants.URL + slug);
                done();
            });
        });

但现在，这是我的错误：

it('should have called the fetch function wih the good const parameter and slug', done => {
            const slug = 'slug';
            const stubDispatch = () => null;
            const spy = jest.mock('node-fetch', () => Promise.resolve({json: () => []}));
            const dispatcher = fetchRemote(slug);
            dispatcher(stubDispatch).then(() => {
                expect(spy).toHaveBeenCalledWith(Constants.URL + slug);
                done();
            });
        });

Answer 1

首先，您需要在testing async code时返回承诺。而你的间谍需要回复已经解决或被拒绝的承诺。

it('should have called the fetch function wih the good const parameter and slug', done => {
  const slug = 'successPath';
  const stubDispatch = () => Promise.resolve({ json: () => [] });
  spy = jest.mock('node-fetch', (path) => {
    if (path === Constants.URL + 'successPath') {
      return Promise.resolve('someSuccessData ')
    } else {
      return Promise.reject('someErrorData')
    }
  });
  const dispatcher = fetchRemote(slug);
  return dispatcher(stubDispatch).then(() => {
    expect(spy).toHaveBeenCalledWith(Constants.URL + slug);
    done();
  });
});

与Jest嘲笑承诺的基本要求

1 个答案: