Question

我正在尝试模拟一个名为callApi的函数。我使用jest.fn（），但出现错误消息：

函数callApi（方法：字符串，url：字符串，路径：字符串，数据？：任何）：承诺> 无法分配“ callApi”，因为它是只读属性。ts（2540）

我尝试遵循以下示例 jest examples

我的代码有什么问题？为什么会出现错误消息。
callApi的一部分是从“ axios”导入axios；

export function callApi(
  method: string,
  url: string,
  path: string,
  data?: any
) {
  switch (method) {

测试如下：

import {runSaga} from 'redux-saga';
import * as api from '../Utilities/api'
import { getPaymentsError, getPaymentsSuccess, IPaymentsAction } from './actions';
import handleFetch from './sagas'


test('should test fetch payments success',async() =>{
const dispatchedActions = [{}];
const mockedPayments = [{
    details: {
    amount: "10000",
    date: new Date(),
    id: 5
  },
  id: 5,
  month: "Feb 2003",
  userID: 3
}];


 api.callApi = jest.fn(() => Promise.resolve(mockedPayments));<----------error here



const fakeStore = {
    dispatch:(action:IPaymentsAction) =>dispatchedActions.push(action)
}
await runSaga(fakeStore,handleFetch).done;
expect(api.callApi.mock.calls.length).toBe(1);
expect(dispatchedActions).toContainEqual(getPaymentsSuccess(mockedPayments));
})

Answer 1

分配给jest.fn()不适用于TypeScript输入。

改为使用jest.spyOn：

test('should test fetch payments success', async (done) => {
  const dispatchedActions = [{}];
  const mockedPayments = [{
    details: {
      amount: "10000",
      date: new Date(),
      id: 5
    },
    id: 5,
    month: "Feb 2003",
    userID: 3
  }];

  const spy = jest.spyOn(api, 'callApi');
  spy.mockImplementation(() => Promise.resolve(mockedPayments));

  const fakeStore = {
    dispatch: (action: IPaymentsAction) => dispatchedActions.push(action)
  }
  await runSaga(fakeStore, handleFetch);done();
  expect(spy.mock.calls.length).toBe(1);
  expect(dispatchedActions).toContainEqual(getPaymentsSuccess(mockedPayments));
})

如何使用jest.fn（）

1 个答案: