new_contents: from django.test import TestCase
  from django.contrib.admin.sites import AdminSite
  
  from coupons.admin import CouponAdmin
  from coupons.models import Coupon
  
  
  class MockRequest(object):
      pass
  
  
  request = MockRequest()
  
  
  class CouponAdminTestCase(TestCase):
      def setUp(self):
          self.site = AdminSite()
  
      def test_list_display(self):
          admin = CouponAdmin(Coupon, self.site)
  
          self.assertEquals(
              list(admin.get_fields(request)),
              ['value', 'code', 'type', 'user', 'redeemed_at', 'valid_until', 'campaign']
          )
  
subject: add test case for admin list display of coupon admin