javascript - 如何测试使用 setTimeout 调用另一个 Action 的异步 Action 创建者

Question

我有以下显示通知然后将其删除的操作，我正在尝试为其编写单元测试，但我似乎无法弄清楚如何模拟 setTimeout。

export const addNotification = (text, notificationType = 'success', time = 4000) => {
        return (dispatch, getState) =>{
            let newId = new Date().getTime();
            dispatch({
                type: 'ADD_NOTIFICATION',
                notificationType,
                text,
                id: newId
            });
            setTimeout(()=>{
                dispatch(removeNotification(newId))
            }, time)
        }
    };
    export const removeNotification = (id) => (
    {
        type: 'REMOVE_NOTIFICATION',
        id
    });

按照 redux 网站上关于异步测试的教程，我想出了以下测试:

    import * as actions from '../../client/actions/notifyActionCreator'
    import configureMockStore from 'redux-mock-store'
    import thunk from 'redux-thunk'

    const middlewares = [ thunk ];
    const mockStore = configureMockStore(middlewares);


    describe('actions', ()=>{

        it('should create an action to add a notification and then remove it', ()=>{

            const store = mockStore({ notifications:[] });

            const text = 'test action';
            const notificationType = 'success';
            const time = 4000;
            const newId = new Date().getTime();

            const expectedActions = [{
                type: 'ADD_NOTIFICATION',
                notificationType,
                text,
                id: newId
            },{
                type: 'REMOVE_NOTIFICATION',
                id: newId
            }];

            return store.dispatch(actions.addNotification(text,notificationType,time))
                .then(() => {
                    expect(store.getActions()).toEqual(expectedActions)
                });
        });
    });

现在它只是抛出一个错误 Cannot read property 'then' of undefined at store.dispatch，任何帮助将不胜感激。

Answer 1

首先，因为你的 action creator 不返回任何东西，当你调用 store.dispatch(actions.addNotification()) 它返回 undefined 这就是你的原因收到错误 Cannot read property 'then' of undefined。要使用 .then()，它应该返回一个 promise。

因此，您应该修复 Action 创建者或测试以反射(reflect) Action 创建者实际执行的操作。为了让你的测试通过，你可以把你的测试改成这样:

// set up jest's fake timers so you don't actually have to wait 4s
jest.useFakeTimers();

store.dispatch(actions.addNotification(text,notificationType,time));
jest.runAllTimers();
expect(store.getActions()).toEqual(expectedActions);

另一种选择是使用详细的策略 in the Jest docs .

// receive a function as argument
test('should create an action to add a notification and then remove it', (done)=>{

    // ...

    store.dispatch(actions.addNotification(text,notificationType,time));
    setTimeout(() => {
      expect(store.getActions()).toEqual(expectedActions);
      done();
    }, time);
});

当使用这个策略时，Jest 将等待 done() 被调用，否则它会在测试主体执行完成时认为测试结束。