Fix broken functional tests!

I forgot to modify the test config to account for django-compressor.

tests/config.py

                 'django.contrib.sites',
                 'django.contrib.flatpages',
                 'sorl.thumbnail',
+                'compressor',
                 ] + OSCAR_CORE_APPS,
             TEMPLATE_CONTEXT_PROCESSORS=(
                 "django.contrib.auth.context_processors.auth",
             },
             ROOT_URLCONF='tests._site.urls',
             LOGIN_REDIRECT_URL='/accounts/',
+            STATIC_URL='/static/',
+            COMPRESS_ENABLED=False,
             DEBUG=False,
             SITE_ID=1,
             APPEND_SLASH=True,

tests/unit/offer/custom_benefit_tests.py

+from decimal import Decimal as D
+
+from django.test import TestCase
+from django.contrib.auth.models import User
+from django_dynamic_fixture import G
+import mock
+
+from oscar.apps.offer import custom, models
+from oscar.apps.basket.models import Basket
+
+
+class ChangesOwnerName(models.Benefit):
+
+    class Meta:
+        proxy = True
+
+    def apply(self, basket, condition, offer=None):
+        basket.owner.first_name = "Terry"
+        basket.owner.save()
+        return D('0.00')
+
+    @property
+    def description(self):
+        return 'Changes owners name'
+
+
+class NoDescription(models.Benefit):
+
+    class Meta:
+        proxy = True
+
+    def apply(self, basket, condition, offer=None):
+        return D('0.00')
+
+
+class TestACustomBenefit(TestCase):
+
+    def test_must_implement_a_description_property(self):
+        with self.assertRaises(RuntimeError):
+            custom.create_benefit(NoDescription)
+
+
+class TestCustomBenefit(TestCase):
+
+    def setUp(self):
+        self.benefit = custom.create_benefit(ChangesOwnerName)
+        self.condition = mock.Mock()
+        self.basket = Basket()
+
+    def test_applies_correctly(self):
+        self.basket.owner = G(User, first_name="Alan")
+        self.benefit.proxy().apply(self.basket, self.condition)
+        self.assertEqual("Terry", self.basket.owner.first_name)