sagas

login.js

// @flow
import { put, call, takeLatest } from 'redux-saga/effects';
import { login as loginApi } from '../api/login';
import {
  loginActionTypes,
  loginLoading,
  loginComplete,
  loginInvalid
} from '../reducers/login/loginActions';
import type { UserLogin } from '../reducers/login/loginActions';

export function* login(action: UserLogin): Generator<*, *, *> {
  const { username, password } = action.payload;
  yield put(loginLoading());
  try {
    const loginSuccess: boolean = yield call(loginApi, username, password);
    if (loginSuccess) {
      yield put(loginComplete());
    } else {
      yield put(loginInvalid());
    }
  } catch (e) {}
}

function* watchLogin(): Generator<*, *, *> {
  yield takeLatest(userActionTypes.login, login);
}
export default [watchLogin]; // import array into root saga to run

login.test.js

// @flow
import { put, call } from 'redux-saga/effects';
import { cloneableGenerator } from 'redux-saga/utils';
import {
  login as loginActionCreator,
  loginInvalid,
  loginLoading,
  loginComplete,
} from '../reducers/login/loginActions';
import { login as loginApi } from '../api/login';
import { login } from './login';

const username = 'testUser';
const password = 'testPassword';
const loginAction = loginActionCreator({ username, password });

describe('login flow', () => {
  const generator = cloneableGenerator(login)(loginAction);
  expect(generator.next().value).toEqual(put(loginLoading()));
  expect(generator.next().value).toEqual(call(loginApi, username, password));

  test('credentials success', () => {
    const clone = generator.clone();
    expect(clone.next(true).value).toEqual(put(loginComplete()));
    expect(clone.next().done).toEqual(true);
  });

  test('or credentials invalid', () => {
    const clone = generator.clone();
    expect(clone.next(false).value).toEqual(put(loginInvalid()));
    expect(clone.next().done).toEqual(true);
  });
});