Jest测试Redux异步Action时Catch块Dispatch未触发问题求助

我正在用Jest和Enzyme测试React+Redux课程项目，测试Redux Action时遇到了问题：

有一个requestRobots函数负责异步数据获取，基于Promise结果在then/catch逻辑中分发Action，由redux-thunk中间件处理。实际项目中出错时，Catch块能正常分发失败Action，但Jest测试时，错误虽被捕获并打印，Catch块内的dispatch却未触发。我用redux-mock-store搭建了Mock Redux Store，代码中的apiCall是fetch API的抽象封装。

相关代码 #

action.test.js

it("Test request robots action when called - unsuccessful state", async () => {
  const apiCall = jest.fn().mockReturnValue(Promise.reject("Not found"));
  const store = mockStore();
  await store.dispatch(actions.requestRobots(apiCall));
  const action = store.getActions();
  console.log(action);
  expect(apiCall).toBeCalled();
  expect(apiCall.mock.calls.length).toBeGreaterThan(0);
  console.log(apiCall.mock);
});

action.js

export const requestRobots = apiCall => dispatch => {
  dispatch({ type: REQUEST_ROBOTS_PENDING });
  apiCall("https://jsonplaceholder.typicode.com/users")
    .then(data => dispatch({ type: REQUEST_ROBOTS_SUCCESS, payload: data }))
    .catch(error => {
      console.log(error);
      dispatch({ type: REQUEST_ROBOTS_FAILED, payload: error });
    });
};

测试输出日志（翻译后） #

console.log: action: [ { type: 'REQUEST_ROBOTS_PENDING' } ]
console.log: Not found
测试通过，但未捕获到REQUEST_ROBOTS_FAILED类型的Action

问题原因及解决方案 #

问题根源在于requestRobots没有返回Promise链，导致测试中的await无法等待异步操作完成。当执行await store.dispatch(actions.requestRobots(apiCall))时，dispatch会立即返回，此时Catch块里的dispatch还未执行，所以store.getActions()只能拿到REQUEST_ROBOTS_PENDING这一个Action。

修复步骤：

1. 修改requestRobots，让它返回apiCall的Promise链：

export const requestRobots = apiCall => dispatch => {
  dispatch({ type: REQUEST_ROBOTS_PENDING });
  // 返回Promise，让await能等待异步流程结束
  return apiCall("https://jsonplaceholder.typicode.com/users")
    .then(data => dispatch({ type: REQUEST_ROBOTS_SUCCESS, payload: data }))
    .catch(error => {
      console.log(error);
      dispatch({ type: REQUEST_ROBOTS_FAILED, payload: error });
    });
};

2. 完善测试断言，验证失败Action是否被正确分发：

it("Test request robots action when called - unsuccessful state", async () => {
  const apiCall = jest.fn().mockReturnValue(Promise.reject("Not found"));
  const store = mockStore();
  await store.dispatch(actions.requestRobots(apiCall));
  const actions = store.getActions();
  
  expect(apiCall).toHaveBeenCalled();
  expect(actions).toEqual([
    { type: 'REQUEST_ROBOTS_PENDING' },
    { type: 'REQUEST_ROBOTS_FAILED', payload: 'Not found' }
  ]);
});

内容的提问来源于stack exchange，提问作者sridarshan