EasilyTestableCart.js

const Cart = ({items, isLoggedIn, btnCallBack}) => {
  
  if(!isLoggedIn){
    return <LoginPrompt/>
  }
  
  return(
    <div>
      <div>
      {items.map(({price, name}) => {
        return(
          <ItemDisplay price={price} name={name}/>  
        )
      })
      <button onClick={() => btnCallback()}>Clear Cart</button>
      </div>
    </div>
  )
}