如何用 Jest 测试这个 Redux Saga 代码？答案

【问题标题】：How to test this Redux Saga code with Jest?如何用 Jest 测试这个 Redux Saga 代码？
【发布时间】：2020-03-21 09:43:45
【问题描述】：

过去，我们使用更容易测试的 Redux Thunk。转换成 Redux-Saga 之后是这样的：

import { takeLatest, put } from "redux-saga/effects";
function* fetchTasksSaga(){
 try {
const taskResponse = yield fetch("API URL")
const tasks = yield taskResponse.json()
yield put(fetchTasksSuccess(tasks));
} catch (error) {
yield put(fetchTasksError(error.message));
  }
}
export default function* watchFetchTasksSaga(){
    yield takeLatest("FETCH_TASKS_START", fetchTasksSaga)
}

对于这个 sn-p，它看起来如何像是一个开玩笑的测试？

【问题讨论】：

标签： reactjs redux react-redux jestjs redux-saga

【解决方案1】：

它看起来像下面的代码：

describe('saga testing watchFetchTasksSaga', () => {
   it('should test watchFetchTasksSaga', () => {
     const gen = watchFetchTasksSaga();
     expect(gen.next().value).toEqual(takeLatest("FETCH_TASKS_START", fetchTasksSaga));
        });
});

describe('test fetchTasksSaga', () => {
    const gen = cloneableGenerator(fetchTasksSaga)();
    expect(gen.next().value).toEqual(fetch("API URL"));

    it('test fetchTasksSaga success scenario', () => {
      const gen1 = gen.clone();
      const data = '2cd09fe0-3b6f-11ea-b05a-3b06a24be1d6';
      const response = { data };
      expect(gen1.next(response).value).toEqual(response.json());
      expect(gen1.next().value).toEqual(
        put(fetchTasksSuccess(tasks)),
      );
      expect(gen1.next().done).toBe(true);
    });

    it('should test error scenario', () => {
      const gen1 = gen.clone();
      const error = {
        message: 'some error',
      };
      expect(gen1.throw(error).value).toEqual(
        put(fetchTasksError(error.message)),
      );
    });
  });

参考：https://redux-saga.js.org/docs/advanced/Testing.html

【讨论】：

@newtech-lover 上面的回答对你有帮助吗？