ShoppingCartWithContainer.js

import apiClient from './apiClient';
import ShoppingCart from './ShoppingCart';
  
const ShoppingCartContainer = ({apiClient}) => {
  const [errorMessage, setErrorMessage] = useState(null)
  const isLoggedIn = useSelector((state) => state.account.isLoggedIn);
  
  const urlToUse = isLoggedIn ? 'https://api/customercheckout' : 'https://api/guestcheckout';
  
  const addToCartFunction = async (items) => {
    const { data, errors } = await apiClient(urlToUse, {items});
    if(errors){
      setErrorMessage('Oops, something went wrong...')
    }
  }

  return(
    <ShoppingCart 
      errorMessage={errorMessage} 
      addToCartFunction={addToCartFunction}
    />
  )      
}

ShoppingCartContainer.defaultProps = {
  apiClient
}
  
// Now our shopping cart is much simpler to test as well as the container

const ShoppingCart = ({addToCartFunction, isLoggedIn, errorMessage}) => {

  return ...
}