javascript - 使用带有 take 和 delay 的 runSaga 进行测试

Question

如果我有一个具有这种形式的传奇:

function * sagaWorker() {
  yield put(START_ACTION)
  yield take(WAIT_FOR_ACTION)
  yield delay(100)
  yield put(END_ACTION)
}

我可以像这样使用 runSaga 成功测试它:

step('saga passes the tests', async () => {
  const channel = stdChannel()
  const dispatched = []
  const options = {
    dispatch: action => dispatched.push(action),
    getState: () => {},
    channel
  }
  const task = runSaga(options, sagaWorker)
  channel.put(WAIT_FOR_ACTION)
  await task.toPromise()
  expect(dispatched).to.deep.eql([START_ACTION, END_ACTION])
})

但是，如果我将延迟移到镜头前:

function * sagaWorker() {
  yield put(START_ACTION)
  yield delay(100)
  yield take(WAIT_FOR_ACTION)
  yield put(END_ACTION)
}

现在 saga 没有运行完成并超时 - 它到达了 take 但操作从未到达 channel 。

是否可以使用此表单对其进行测试？我怀疑我可以通过 calling delay 而不是直接 yield 来让它工作，但我想知道如何制作它在不这样做的情况下工作(如果可能的话)。

Answer 1

使用 yield call(() => myPromiseyDelay(500)) 不会在此处保存您。派发时仍然不会注意到“丢失”操作。

当您发布WAIT_FOR_ACTION 时，saga 在yield delay 时处于已屈服状态。这里没有 Action 队列，所以当你到达 yield take(WAIT_FOR_ACTION) 时，WAIT_FOR_ACTION Action 早已被调度，没有被任何 saga 注意到您在上面提出的逻辑(没有事件的 take 来获取操作)。

考虑设置一个 actionChannel捕捉这些未听的 Action 。在 delay 完成后，它们将在 channel 中排队等待消费。

所以，像这样:

function * sagaWorker() {
  const channel = yield actionChannel(WAIT_FOR_ACTION)
  yield put(START_ACTION)
  yield delay(100)
  yield take(channel)
  yield put(END_ACTION)
}

所以把这些放在一起作为非伪代码:

const {
  runSaga,
  stdChannel,
  effects: {
    take,
    put,
    actionChannel,
    delay
  }
} = window.ReduxSaga

const WAIT_FOR_ACTION = "WAIT_FOR_ACTION";
const START_ACTION = "START_ACTION";
const END_ACTION = "END_ACTION";

(async() => {
  const channel = stdChannel();
  const dispatched = [];
  const options = {
    dispatch: action => dispatched.push(action),
    getState: () => {},
    channel
  };
  const task = runSaga(options, sagaWorker);
  channel.put({
    type: WAIT_FOR_ACTION
  });
  await task.toPromise();
  console.log(dispatched);
})();

function* sagaWorker() {
  const channel = yield actionChannel(WAIT_FOR_ACTION);
  yield put({
    type: START_ACTION
  });
  yield delay(100);
  yield take(channel);
  yield put({
    type: END_ACTION
  });
}

<script src="https://cdn.jsdelivr.net/npm/redux-saga@1.1.3/dist/redux-saga.umd.min.js"></script>