Javascript 在if语句中测试redux saga并使用实际值

如何在if语句或try/catch中测试函数？比如说,

export function* onFetchMessages(channel) {
    yield put(requestMessages())
    const channel_name = channel.payload
    try {
        const response = yield call(fetch,'/api/messages/'+channel_name)

        if(response.ok){
            const res = yield response.json();

            const date = moment().format('lll');
            yield put(receiveMessages(res,channel.payload,date))
        }


    } catch (error){
        yield put(rejectMessages(error))
    }
}

我需要输入一个实际存在于数据库中的通道名，以便它返回一个有效的响应来执行后续的输出，否则它将抛出一个错误。此外，我将收到一条错误消息，无法读取未定义的json属性，因此由于此错误消息，无法达到该属性之后的收益率。 所以我的第一个问题是“ifresponse.ok”，但即使我删除它，yield response.json也会返回一个错误，而且之后的yield将不会执行。

---

如果有人能告诉我如何测试这些，我将不胜感激。

将响应对象传递给上一次执行并测试条件，我会这样做，希望这有帮助：

 export function* onFetchMessages(channel) {
try {
    yield put(requestMessages())
    const channel_name = channel.payload
    const response = yield call(fetch,'/api/messages/'+channel_name)

    if(response.ok){
        const res = yield response.json();

        const date = moment().format('lll');
        yield put(receiveMessages(res,channel.payload,date))
    }

   } catch (error){
      yield put(rejectMessages(error))
  }
}

describe('onFetchMessages Saga', () => {
 let output = null;
 const saga = onFetchMessages(channel); //mock channel somewhere...

 it('should put request messages', () => {
  output = saga.next().value;
  let expected = put(requestMessages()); //make sure you import this dependency
  expect(output).toEqual(expected);
 });

 it('should call fetch...blabla', ()=> {
  output = saga.next(channel_name).value; //include channel_name so it is avaiable on the next iteration
  let expected = call(fetch,'/api/messages/'+channel_name); //do all the mock you ned for this
  expect(output).toEqual(expected);
 });

 /*here comes you answer*/
 it('should take response.ok into the if statemenet', ()=> {
  //your json yield is out the redux-saga context so I dont assert it
   saga.next(response).value; //same as before, mock it with a ok property, so it is available
   output = saga.next(res).value; //assert the put effect
   let expected = put(receiveMessages(res,channel.payload,date)); //channel should be mock from previous test
   expect(output).toEqual(expected);
 });

});

---

请注意，您的代码可能做了更多我不知道的事情，但这至少应该让您有时间来解决您的问题。

您可能需要为此使用一个帮助程序库，例如

免责声明：我编写此库是为了解决完全相同的问题

对于您的具体示例，使用Jest，但对摩卡的效果相同，我将做两件事：

首先，我将API调用分离到不同的函数 然后我将使用redux saga测试以同步方式测试您的逻辑： 代码如下：

import sagaHelper from 'redux-saga-testing';
import { call, put } from 'redux-saga/effects';
import { requestMessages, receiveMessages, rejectMessages } from './my-actions';

const api = url => fetch(url).then(response => {
    if (response.ok) {
        return response.json();
    } else {
        throw new Error(response.status); // for example
    }
});

function* onFetchMessages(channel) {
    try {
        yield put(requestMessages())
        const channel_name = channel.payload
        const res = yield call(api, '/api/messages/'+channel_name)
        const date = moment().format('lll');

        yield put(receiveMessages(res,channel.payload,date))
    } catch (error){
        yield put(rejectMessages(error))
    }
}


describe('When testing a Saga that throws an error', () => {
    const it = sagaHelper(onFetchMessages({ type: 'foo', payload: 'chan1'}));

    it('should have called the API first, which will throw an exception', result => {
        expect(result).toEqual(call(api, '/api/messages/chan1'));
        return new Error('Something went wrong');
    });

    it('and then trigger an error action with the error message', result => {
        expect(result).toEqual(put(rejectMessages('Something went wrong')));
    });
});

describe('When testing a Saga and it works fine', () => {
    const it = sagaHelper(onFetchMessages({ type: 'foo', payload: 'chan2'}));

    it('should have called the API first, which will return some data', result => {
        expect(result).toEqual(call(api, '/api/messages/chan2'));
        return 'some data';
    });

    it('and then call the success action with the data returned by the API', result => {
        expect(result).toEqual(put(receiveMessages('some data', 'chan2', 'some date')));
        // you'll have to find a way to mock the date here'
    });
});

---

你会在

上找到很多其他更复杂的例子，这里有一个相关的问题：在redux saga文档中，他们有take正在监听多个动作的例子。基于此，我编写了一个auth saga，大致如下您可能会发现这是redux saga文档中示例的修改版本：

---

我不认为在处理Sagas时这是一种反模式，并且代码在测试环境Jest之外确实按预期运行。但是，我看不到在这种上下文中处理if语句的方法。这是怎么回事？

谢谢，用ok属性模仿回应似乎是个计划，但你会怎么做？如果你能把最后一部分编码出来，那就太好了，因为这才是真正重要的部分传递一个像saga.next{ok:true}.value这样的对象

function* mySaga() { 
    while (true) {
        const initialAction = yield take (['AUTH__LOGIN','AUTH__LOGOUT']);
        if (initialAction.type === 'AUTH__LOGIN') {
            const authTask = yield fork(doLogin);
            const action = yield take(['AUTH__LOGOUT', 'AUTH__LOGIN_FAIL']);
            if (action.type === 'AUTH__LOGOUT') {
                yield cancel(authTask);
                yield call (unauthorizeWithRemoteServer)
            }
        } else {
            yield call (unauthorizeWithRemoteServer)
        }
    }
}