Refs #340 -- Allow order changes for paid orders if they don't change the total

src/tests/base/test_orders.py

@@ -140,6 +140,8 @@ class OrderChangeManagerTests(TestCase):
         )
         self.ticket = Item.objects.create(event=self.event, name='Early-bird ticket', tax_rate=Decimal('7.00'),
                                           default_price=Decimal('23.00'), admission=True)
+        self.ticket2 = Item.objects.create(event=self.event, name='Other ticket', tax_rate=Decimal('7.00'),
+                                           default_price=Decimal('23.00'), admission=True)
         self.shirt = Item.objects.create(event=self.event, name='T-Shirt', tax_rate=Decimal('19.00'),
                                          default_price=Decimal('12.00'))
         self.op1 = OrderPosition.objects.create(
@@ -303,3 +305,22 @@ class OrderChangeManagerTests(TestCase):
         assert self.order.total == 0
         assert self.order.status == Order.STATUS_PAID
         assert self.order.payment_provider == 'free'
+
+    def test_change_paid_same_price(self):
+        self.order.status = Order.STATUS_PAID
+        self.order.save()
+        self.ocm.change_item(self.op1, self.ticket2, None)
+        self.ocm.commit()
+        self.order.refresh_from_db()
+        assert self.order.total == 46
+        assert self.order.status == Order.STATUS_PAID
+
+    def test_change_paid_different_price(self):
+        self.order.status = Order.STATUS_PAID
+        self.order.save()
+        self.ocm.change_price(self.op1, Decimal('5.00'))
+        with self.assertRaises(OrderError):
+            self.ocm.commit()
+        self.order.refresh_from_db()
+        assert self.order.total == 46
+        assert self.order.status == Order.STATUS_PAID