new_contents: from django.urls import reverse
  from rest_framework import status
  from rest_framework.test import APITestCase
  
  from iati.factory.iati_factory import ActivityFactory, OtherIdentifierFactory
  
  
  class ActivityFiltersTestCase(APITestCase):
  
      def setUp(self):
          self.first_activity = ActivityFactory(
              iati_identifier='XM-DAC-41304-201NEP1000'
          )
  
          self.first_other_identifier = OtherIdentifierFactory(
              activity=self.first_activity,
              identifier='AAA'
          )
  
      def test_other_identifier_filter_single_identifier(self):
          url = reverse('activities:activity-list')
  
          response = self.client.get(url)
          response = self.client.get(
              url, {
                  'other_identifier': self.first_other_identifier.identifier,
              }, format='json'
          )
  
          self.assertTrue(status.is_success(response.status_code))
          self.assertEquals(response.data['count'], 1)
          self.assertEquals(
              response.data['results'][0]['iati_identifier'],
              self.first_activity.iati_identifier
          )
  
      def test_other_identifier_filter_multiple_identifiers(self):
          # Let's create more activities:
          self.second_activity = ActivityFactory(
              iati_identifier='XM-DAC-41304-170GLO4038'
          )
  
          self.second_other_identifier = OtherIdentifierFactory(
              activity=self.second_activity,
              identifier='BBB'
          )
  
          url = reverse('activities:activity-list')
  
          response = self.client.get(url)
          response = self.client.get(
              url, {
                  'other_identifier': '%s,%s' % (
                      self.first_other_identifier.identifier,
                      self.second_other_identifier.identifier
                  )
              }, format='json'
          )
  
          self.assertTrue(status.is_success(response.status_code))
          self.assertEquals(response.data['count'], 2)
          self.assertEquals(
              response.data['results'][0]['iati_identifier'],
              self.first_activity.iati_identifier
          )
          self.assertEquals(
              response.data['results'][1]['iati_identifier'],
              self.second_activity.iati_identifier
          )
  
subject: Add tests for new 'other_identifier' filter