Added test for model using trait

Added readme for CanBeBoughtTrait
https://github.com/Crinsane/LaravelShoppingcart/issues/427

README.md

@@ -329,7 +329,20 @@ $cart->setDiscount($rowId, 21);
 
 ### Buyable
 
-For the convenience of faster adding items to cart and their automatic association, your model can implement `Buyable` interface. To do so, it must implement such functions:
+For the convenience of faster adding items to cart and their automatic association, your model has to implement the `Buyable` interface. You can use the `CanBeBought` trait to implement the required methods but keep in mind that these will use predefined fields on your model for the required values.
+```php
+<?php
+namespace App\Models;
+
+use Gloudemans\Shoppingcart\Contracts\Buyable;
+use Illuminate\Database\Eloquent\Model;
+
+class Product extends Model implements Buyable {
+    use Gloudemans\Shoppingcart\CanBeNought;
+}
+```
+
+If the trait does not work for on the model or you wan't to map the fields manually the model has to implement the `Buyable` interface methods. To do so, it must implement such functions:
 
 ```php
     public function getBuyableIdentifier(){
@@ -341,6 +354,9 @@ For the convenience of faster adding items to cart and their automatic associati
     public function getBuyablePrice(){
         return $this->price;
     }
+    public function getBuyableWeight(){
+        return $this->weight;
+    }
 ```
 
 Example:

tests/CartTest.php

@@ -16,6 +16,7 @@ use Gloudemans\Shoppingcart\ShoppingcartServiceProvider;
 use Gloudemans\Tests\Shoppingcart\Fixtures\ProductModel;
 use Gloudemans\Tests\Shoppingcart\Fixtures\BuyableProduct;
 use Gloudemans\Tests\Shoppingcart\Fixtures\Identifiable;
+use Gloudemans\Tests\Shoppingcart\Fixtures\BuyableProductTrait;
 
 class CartTest extends TestCase
 {
@@ -1096,6 +1097,28 @@ class CartTest extends TestCase
         $this->assertItemsInCart(2, $cart);
     }
 
+    /** @test */
+    public function cart_can_create_items_from_models_using_the_canbebought_trait()
+    {
+        $cart = $this->getCartDiscount( 50 );
+
+        $cart->add(new BuyableProductTrait(1, 'First item', 10.00), 2);
+
+        $cartItem = $cart->get('027c91341fd5cf4d2579b49c4b6a90da');
+
+        $cart->setTax('027c91341fd5cf4d2579b49c4b6a90da', 19);
+
+        $this->assertEquals(10.00, $cartItem->price(2));
+        $this->assertEquals(5.00, $cartItem->discount(2));
+        $this->assertEquals(10.00, $cartItem->discountTotal(2));
+        $this->assertEquals(5.00, $cartItem->priceTarget(2));
+        $this->assertEquals(10.00, $cartItem->subtotal(2));
+        $this->assertEquals(0.95, $cartItem->tax(2));
+        $this->assertEquals(1.90, $cartItem->taxTotal(2));
+        $this->assertEquals(5.95, $cartItem->priceTax(2));
+        $this->assertEquals(11.90, $cartItem->total(2));
+    }
+
     /**
      * Get an instance of the cart.
      *

tests/Fixtures/BuyableProductTrait.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace Gloudemans\Tests\Shoppingcart\Fixtures;
+
+use Gloudemans\Shoppingcart\Contracts\Buyable;
+
+class BuyableProductTrait implements Buyable
+{
+    use \Gloudemans\Shoppingcart\CanBeBought;
+
+    /**
+     * @var int|string
+     */
+    private $id;
+
+    /**
+     * @var string
+     */
+    private $name;
+
+    /**
+     * @var float
+     */
+    private $price;
+
+    /**
+     * @var float
+     */
+    private $weight;
+
+    /**
+     * BuyableProduct constructor.
+     *
+     * @param int|string $id
+     * @param string     $name
+     * @param float      $price
+     */
+    public function __construct($id = 1, $name = 'Item name', $price = 10.00, $weight = 0)
+    {
+        $this->id = $id;
+        $this->name = $name;
+        $this->price = $price;
+        $this->weight = $weight;
+    }
+}