Strange behavior when testing sagas after `call()`.

Hi,

I’m trying to test some simple sagas following the examples in this repository but the tests are giving me strange results. First of all, the code:

sagas/index.js

export function* loadApp() {
  yield put(showLoading());
  const { users, expenses, categories } = yield call(fetchAll);
  yield put(receiveUsers(users));
  yield put(receiveExpenses(expenses));
  yield put(receiveCategories(categories));
  yield put(finishLoading());
}

test/sagas/index.js

describe.skip('#loadApp()', function () {
  const loadAppGenerator = loadApp();
  const users = [{ id: 1 }, { id: 2 }, { id: 3 }];
  const expenses = [{ id: 1 }, { id: 2 }, { id: 3 }];
  const categories = [{ id: 1 }, { id: 2 }, { id: 3 }];

  it('should start yielding SHOW_LOADING action', function () {
    const expected = put(ApplicationActions.showLoading());
    const result = loadAppGenerator.next().value;
    expect(result).to.deep.equal(expected);
  });
  it('should yield a call to api.fetchAll()', function () {
    const expected = call(fetchAll);
    const result = loadAppGenerator.next().value;
    expect(result).to.deep.equal(expected);
  });
  it('should yield action RECEIVE_USERS', function () {
    const expected = put(UsersActions.receiveUsers(users));
    const result = loadAppGenerator.next(users).value;
    expect(result).to.deep.equal(expected);
  });
  it('should yield action RECEIVE_EXPENSES', function () {
    const expected = put(ExpensesActions.receiveExpenses(expenses));
    const result = loadAppGenerator.next(expenses).value;
    expect(result).to.deep.equal(expected);
  });
  it('should yield action RECEIVE_CATEGORIES', function () {
    const expected = put(CategoriesActions.receiveCategories(categories));
    const result = loadAppGenerator.next(categories).value;
    expect(result).to.deep.equal(expected);
  });
  it('should finish yielding FINISH_LOADING action', function () {
    const expected = put(ApplicationActions.finishLoading());
    const result = loadAppGenerator.next().value;
    expect(result).to.deep.equal(expected);
  });
});

In the above example, the first two calls to next() returns a valid state and the tests are passing ok. But, in the third test (when testing RECEIVE_USERS action), when I call loadAppGenerator.next(users).value, it doesn’t pass the users to the action creator. Instead of returning the expected:

PUT: { 
  type: RECEIVE_USERS, 
  payload: { users: [{id:1}, {id:2}, {id:3}] }
}

I’m getting the users as undefined:

PUT: {
  type: RECEIVE_USERS,
  payload: { users: undefined }
}

In other cases is like the next() call was a bit advanced. I have more examples in expenses-api-frontend

[yelouafi]

Yes. Anytime you use the ‘return value’ of yield (e.g via assignament val = yield something, in an expression like if(yield soemthing)), you have to pass the mocked result to the next next call

[Andarist]

@kumar155 Please share ur problem on something like codesandbox.io so we can help you better.