Fix model admin to be instance

jet/tests/admin.py

@@ -1,8 +1,13 @@
 from django.contrib import admin
-from jet.tests.models import TestModel
+from jet.tests.models import TestModel, RelatedToTestModel
 
 
 class TestModelAdmin(admin.ModelAdmin):
     list_display = ('field1', 'field2')
 
+
+class RelatedToTestModelAdmin(admin.ModelAdmin):
+    pass
+
 admin.site.register(TestModel, TestModelAdmin)
+admin.site.register(RelatedToTestModel, RelatedToTestModelAdmin)

jet/tests/test_filters.py

@@ -18,14 +18,11 @@ class FiltersTestCase(TestCase):
         self.models.append(TestModel.objects.create(field1='second', field2=2))
 
     def get_related_field_ajax_list_filter_params(self):
-        class ModelAdmin(admin.ModelAdmin):
-            pass
-
         model = RelatedToTestModel
         field_path = 'field'
         field = get_fields_from_path(model, field_path)[-1]
         lookup_params = {}
-        model_admin = ModelAdmin
+        model_admin = admin.site._registry.get(model)
 
         return field, lookup_params, model, model_admin, field_path