77 - Stubbing the Interface

app/Order.php

@@ -11,6 +11,7 @@ class Order extends Model
     public static function forTickets($tickets, $email, $amount)
     {
         $order = self::create([
+            'confirmation_number' => app(OrderConfirmationNumberGenerator::class)->generate(),
             'email' => $email,
             'amount' => $amount,
         ]);

app/OrderConfirmationNumberGenerator.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace App;
+
+interface OrderConfirmationNumberGenerator
+{
+    public function generate();
+}