corrects tests for latest code changes

bookwyrm/activitypub/base_activity.py

@@ -76,11 +76,12 @@ class ActivityObject:
         if not isinstance(self, model.activity_serializer):
             raise TypeError('Wrong activity type for model')
 
-        # check for an existing instance
-        try:
-            return model.objects.get(remote_id=self.id)
-        except model.DoesNotExist:
-            pass
+        # check for an existing instance, if we're not updating a known obj
+        if not instance:
+            try:
+                return model.objects.get(remote_id=self.id)
+            except model.DoesNotExist:
+                pass
 
         model_fields = [m.name for m in model._meta.get_fields()]
         mapped_fields = {}