TimeToShineSaga.js

import { put, call, select } from 'redux-saga/effects'

export function acquireDataFromSomewhere (numberOfThings) {
  return new Promise((resolve, reject) => {
    resolve(`here are ${numberOfThings} things`)
  })
}

// Fires when we see TIME_TO_SHINE come through.
// Its pretty random what we do here.
// The point is to really show how tests work.
export default function * (action) {

  // step 1
  yield put({ type: 'INCREMENT' })

  // step 2
  const state = yield select()
  const currentCounterValue = state.counter.value

  // step 3
  const data = yield call(
    acquireDataFromSomewhere, 
    currentCounterValue
  )

  // step 4
  yield put({type: 'SAVE_DATA', randomPieceOfData: data})
}