test.js

import expect from 'expect';
import AppConstants from '../../../app/AppConstants';
import store from '../../store';
import { selectLastReadMessageByChannelId } from './channelSelectors';

describe('channel', () => {
  it('should store the messageId when clearing unreads', () => {
    const channelId = 1;
    const messageId = 2;
    store.dispatch({
      type: AppConstants.CHANNEL_UNREADS_CLEARED,
      payload: {
        id: channelId,
        messageId
      }
    });
    expect(selectLastReadMessageByChannelId(store.getState(), channelId)).toEqual(messageId);
  });
});

(there are times I look at how simple my reducers--and everything else in a react redux app--are to think about and wonder why I'm even writing tests at all ...)