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用jest和假定时器测试递归轮询函数

jestjs javascript

VivekN · 技术社区 · 6 年前

我已经创建了一个轮询服务,它递归地调用一个api,如果满足某些条件,那么在api成功时,它会再次保持轮询。

/**
   * start a timer with the interval specified by the user || default interval
   * we are using setTimeout and not setinterval because a slow back end server might take more time than our interval time and that would lead to
   * a queue of ajax requests with no response at all.
   * -----------------------------------------
   * This function would call the api first time and only on the success response of the api we would poll again after the interval
   */
  runPolling() {
    const { url, onSuccess, onFailure, interval } = this.config;
    const _this = this;
    this.poll = setTimeout(() => {
      /* onSuccess would be handled by the user of service which would either return true or false
      * true - This means we need to continue polling
      * false - This means we need to stop polling
      */
      api
        .request(url)
        .then(response => {
          console.log('I was called', response);
          onSuccess(response);
        })
        .then(continuePolling => {
          _this.isPolling && continuePolling ? _this.runPolling() : _this.stopPolling();
        })
        .catch(error => {
          if (_this.config.shouldRetry && _this.config.retryCount > 0) {
            onFailure && onFailure(error);
            _this.config.retryCount--;
            _this.runPolling();
          } else {
            onFailure && onFailure(error);
            _this.stopPolling();
          }
        });
    }, interval);
  }

在尝试为它编写测试用例时,我不太确定如何模拟假计时器和axios api响应。

这就是我目前所拥有的

import PollingService from '../PollingService';
import { statusAwaitingProduct } from '@src/__mock_data__/getSessionStatus';
import mockAxios from 'axios';

describe('timer events for runPoll', () => {
    let PollingObject,
    pollingInterval = 3000,
    url = '/session/status',
    onSuccess = jest.fn(() => {
      return false;
    });
    beforeAll(() => {
      PollingObject = new PollingService({
        url: url,
        interval: pollingInterval,
        onSuccess: onSuccess
      });
    });
    beforeEach(() => {
      jest.useFakeTimers();
    });
    test('runPolling should be called recursively when onSuccess returns true', async () => {
      expect.assertions(1);
      const mockedRunPolling = jest.spyOn(PollingObject, 'runPolling');
      const mockedOnSuccess = jest.spyOn(PollingObject.config, 'onSuccess');
      mockAxios.request.mockImplementation(
        () =>
          new Promise(resolve => {
            resolve(statusAwaitingProduct);
          })
      );

      PollingObject.startPolling();
      expect(mockedRunPolling).toHaveBeenCalledTimes(1);
      expect(setTimeout).toHaveBeenCalledTimes(1);
      expect(mockAxios.request).toHaveBeenCalledTimes(0);
      expect(setTimeout).toHaveBeenLastCalledWith(expect.any(Function), pollingInterval);

      jest.runAllTimers();
      expect(mockAxios.request).toHaveBeenCalledTimes(1);
      expect(mockedOnSuccess).toHaveBeenCalledTimes(1);
      expect(PollingObject.isPolling).toBeTruthy();
      expect(mockedRunPolling).toHaveBeenCalledTimes(2);
    });
  });
});

有人能帮忙吗? 谢谢

1 回复 | 直到 6 年前

Brian Adams 6 年前

发行

你的测试可能还有其他问题,但我会回答你问的具体问题 expect(mockedOnSuccess).toHaveBeenCalledTimes(1); 失败于 0 times :

jest.runAllTimers 将同步运行任何挂起的计时器回调,直到没有剩余时间为止。这将执行用调度的匿名函数 setTimeout 在内部 runPolling . 当匿名函数执行时,它将调用 api.request(url) 这就是将要发生的一切 . 匿名函数中的所有其他内容都包含在 then get queued in the PromiseJobs Jobs Queue introduced with ES6 . 到那时这些工作都不会执行 开玩笑。运行计时器

expect(mockAxios.request).toHaveBeenCalledTimes(1); 然后就过去了 api.请求(url) 已经执行。

expect(mockedOnSuccess)to havebeen calledTimes(1); 然后就失败了 然后 本该调用它的回调仍在 承诺工作 排队,尚未执行。

解决方案

解决方法是确保作业排队在断言之前有机会逃跑吗 mockedOnSuccess 被叫来了。

承诺工作 async 测试 Jest await Promise.resolve(); 承诺工作 并允许队列中的任何挂起作业首先执行:

test('runPolling should be called recursively when onSuccess returns true', async () => {
  ...
  jest.runAllTimers();
  await Promise.resolve();  // allow any pending jobs in PromiseJobs to execute
  expect(mockAxios.request).toHaveBeenCalledTimes(1);
  expect(mockedOnSuccess).toHaveBeenCalledTimes(1); // SUCCESS
  ...
}

设置超时 因此,没有办法回报一个让考试等待的承诺。

还请注意,您有多个链接 然后 承诺工作 在你的测试中多次。

here .