在if语句中测试redux-saga并使用实值

testing redux-saga inside if statement and using real values

本文关键字：redux-saga if 语句 测试      更新时间：2023-09-26

如何在if语句或try/catch中测试函数?例如,

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))
    }
}

我需要输入数据库中实际存在的真实通道名称，以便它为随后要执行的yield返回有效响应，否则它将抛出错误。此外，我会得到一个错误消息，无法读取未定义的属性json，因此由于此错误消息，无法达到yield。所以我的第一个问题是'if(response.ok)'，但即使我删除它，yield response.json()会返回一个错误，此外yield之后不会被执行。如果有人能告诉我如何测试这些，我将不胜感激。

将响应对象传递给先前的执行和测试条件，我会这样做，希望这有助于:

 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);
 });
});

注意到你的代码可能做了更多我没有意识到的事情，但这至少应该把u放在一些行来解决你的问题。

您可能需要使用辅助库，例如redux-saga-testing。

免责声明:我编写这个库是为了解决完全相同的问题

对于您的特定示例，使用Jest(但对Mocha也一样)，我将做两件事:

  • 首先，我会将API调用分离到不同的函数
    • 然后我会使用redux-saga-testing以同步的方式测试你的逻辑:

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'
    });
});

你会在项目的GitHub上找到很多其他的例子(更复杂的)

这里有一个相关的问题:在redux-saga文档中，他们有take侦听多个操作的示例。基于此，我写了一个授权传奇，看起来或多或少像这样(你可能会意识到这是redux-saga文档中一个例子的修改版本:

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)
        }
    }
}

我不认为在处理saga时这是一个反模式，并且代码当然在测试环境之外按照预期运行(开玩笑)。但是，我认为没有办法在这种上下文中处理if语句。这是怎么回事?

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