Unit test the unallowed transitions, error message on admin, and side effects of successful transitions

src/registrar/tests/test_admin.py

@@ -1,5 +1,8 @@
 from django.test import TestCase, RequestFactory, Client
 from django.contrib.admin.sites import AdminSite
+from unittest.mock import patch
+from contextlib import ExitStack
+from django.contrib import messages
 
 from registrar.admin import (
     DomainApplicationAdmin,
@@ -10,6 +13,7 @@ from registrar.admin import (
 from registrar.models import (
     DomainApplication,
     DomainInformation,
+    Domain,
     User,
     DomainInvitation,
 )
@@ -432,8 +436,159 @@ class TestDomainApplicationAdmin(TestCase):
                 request,
                 "Cannot edit an application with a restricted creator.",
             )
+            
+    def test_error_when_saving_approved_to_rejected_and_domain_is_active(self):
+        # Create an instance of the model
+        application = completed_application(status=DomainApplication.APPROVED)
+        domain = Domain.objects.create(name=application.requested_domain.name)
+        application.approved_domain = domain
+        application.save()
 
+        # Create a request object with a superuser
+        request = self.factory.post(
+            "/admin/registrar/domainapplication/{}/change/".format(application.pk)
+        )
+        request.user = self.superuser
+        
+        # Define a custom implementation for is_active
+        def custom_is_active(self):
+            return True  # Override to return True
+        
+       # Use ExitStack to combine patch contexts
+        with ExitStack() as stack:
+            # Patch Domain.is_active and django.contrib.messages.error simultaneously
+            stack.enter_context(patch.object(Domain, 'is_active', custom_is_active))
+            stack.enter_context(patch.object(messages, 'error'))
+                        
+            # Simulate saving the model
+            application.status = DomainApplication.REJECTED            
+            self.admin.save_model(request, application, None, True)
+
+            # Assert that the error message was called with the correct argument
+            messages.error.assert_called_once_with(
+                request,
+                "This action is not permitted, the domain "
+                + "is already active.",
+            )
+        
+    def test_side_effects_when_saving_approved_to_rejected(self):
+        # Create an instance of the model
+        application = completed_application(status=DomainApplication.APPROVED)
+        domain = Domain.objects.create(name=application.requested_domain.name)
+        domain_information = DomainInformation.objects.create(creator=self.superuser, domain=domain)
+        application.approved_domain = domain
+        application.save()
+
+        # Create a request object with a superuser
+        request = self.factory.post(
+            "/admin/registrar/domainapplication/{}/change/".format(application.pk)
+        )
+        request.user = self.superuser
+        
+        # Define a custom implementation for is_active
+        def custom_is_active(self):
+            return False  # Override to return False
+        
+       # Use ExitStack to combine patch contexts
+        with ExitStack() as stack:
+            # Patch Domain.is_active and django.contrib.messages.error simultaneously
+            stack.enter_context(patch.object(Domain, 'is_active', custom_is_active))
+            stack.enter_context(patch.object(messages, 'error'))
+                        
+            # Simulate saving the model
+            application.status = DomainApplication.REJECTED            
+            self.admin.save_model(request, application, None, True)
+
+            # Assert that the error message was never called
+            messages.error.assert_not_called()
+        
+        self.assertEqual(application.approved_domain, None)
+        
+        # Assert that Domain got Deleted
+        with self.assertRaises(Domain.DoesNotExist):
+            domain.refresh_from_db()
+        
+        # Assert that DomainInformation got Deleted
+        with self.assertRaises(DomainInformation.DoesNotExist):
+            domain_information.refresh_from_db()
+        
+    def test_error_when_saving_approved_to_ineligible_and_domain_is_active(self):
+        # Create an instance of the model
+        application = completed_application(status=DomainApplication.APPROVED)
+        domain = Domain.objects.create(name=application.requested_domain.name)
+        application.approved_domain = domain
+        application.save()
+
+        # Create a request object with a superuser
+        request = self.factory.post(
+            "/admin/registrar/domainapplication/{}/change/".format(application.pk)
+        )
+        request.user = self.superuser
+        
+        # Define a custom implementation for is_active
+        def custom_is_active(self):
+            return True  # Override to return True
+        
+       # Use ExitStack to combine patch contexts
+        with ExitStack() as stack:
+            # Patch Domain.is_active and django.contrib.messages.error simultaneously
+            stack.enter_context(patch.object(Domain, 'is_active', custom_is_active))
+            stack.enter_context(patch.object(messages, 'error'))
+                        
+            # Simulate saving the model
+            application.status = DomainApplication.INELIGIBLE            
+            self.admin.save_model(request, application, None, True)
+
+            # Assert that the error message was called with the correct argument
+            messages.error.assert_called_once_with(
+                request,
+                "This action is not permitted, the domain "
+                + "is already active.",
+            )
+        
+    def test_side_effects_when_saving_approved_to_ineligible(self):
+        # Create an instance of the model
+        application = completed_application(status=DomainApplication.APPROVED)
+        domain = Domain.objects.create(name=application.requested_domain.name)
+        domain_information = DomainInformation.objects.create(creator=self.superuser, domain=domain)
+        application.approved_domain = domain
+        application.save()
+
+        # Create a request object with a superuser
+        request = self.factory.post(
+            "/admin/registrar/domainapplication/{}/change/".format(application.pk)
+        )
+        request.user = self.superuser
+        
+        # Define a custom implementation for is_active
+        def custom_is_active(self):
+            return False  # Override to return False
+        
+       # Use ExitStack to combine patch contexts
+        with ExitStack() as stack:
+            # Patch Domain.is_active and django.contrib.messages.error simultaneously
+            stack.enter_context(patch.object(Domain, 'is_active', custom_is_active))
+            stack.enter_context(patch.object(messages, 'error'))
+                        
+            # Simulate saving the model
+            application.status = DomainApplication.INELIGIBLE            
+            self.admin.save_model(request, application, None, True)
+
+            # Assert that the error message was never called
+            messages.error.assert_not_called()
+        
+        self.assertEqual(application.approved_domain, None)
+        
+        # Assert that Domain got Deleted
+        with self.assertRaises(Domain.DoesNotExist):
+            domain.refresh_from_db()
+        
+        # Assert that DomainInformation got Deleted
+        with self.assertRaises(DomainInformation.DoesNotExist):
+            domain_information.refresh_from_db()
+            
     def tearDown(self):
+        Domain.objects.all().delete()
         DomainInformation.objects.all().delete()
         DomainApplication.objects.all().delete()
         User.objects.all().delete()