diff --git a/bookwyrm/tests/activitypub/test_base_activity.py b/bookwyrm/tests/activitypub/test_base_activity.py
new file mode 100644
index 00000000..865e1638
--- /dev/null
+++ b/bookwyrm/tests/activitypub/test_base_activity.py
@@ -0,0 +1,81 @@
+''' tests the base functionality for activitypub dataclasses '''
+from dataclasses import dataclass
+from django.test import TestCase
+
+from bookwyrm.activitypub.base_activity import ActivityObject, \
+    find_existing_by_remote_id
+from bookwyrm.activitypub import ActivitySerializerError
+from bookwyrm import models
+
+class BaseActivity(TestCase):
+    ''' the super class for model-linked activitypub dataclasses '''
+    def test_init(self):
+        ''' simple successfuly init '''
+        instance = ActivityObject(id='a', type='b')
+        self.assertTrue(hasattr(instance, 'id'))
+        self.assertTrue(hasattr(instance, 'type'))
+
+    def test_init_missing(self):
+        ''' init with missing required params '''
+        with self.assertRaises(ActivitySerializerError):
+            ActivityObject()
+
+    def test_init_extra_fields(self):
+        ''' init ignoring additional fields '''
+        instance = ActivityObject(id='a', type='b', fish='c')
+        self.assertTrue(hasattr(instance, 'id'))
+        self.assertTrue(hasattr(instance, 'type'))
+
+    def test_init_default_field(self):
+        ''' replace an existing required field with a default field '''
+        @dataclass(init=False)
+        class TestClass(ActivityObject):
+            ''' test class with default field '''
+            type: str = 'TestObject'
+
+        instance = TestClass(id='a')
+        self.assertEqual(instance.id, 'a')
+        self.assertEqual(instance.type, 'TestObject')
+
+    def test_serialize(self):
+        ''' simple function for converting dataclass to dict '''
+        instance = ActivityObject(id='a', type='b')
+        serialized = instance.serialize()
+        self.assertIsInstance(serialized, dict)
+        self.assertEqual(serialized['id'], 'a')
+        self.assertEqual(serialized['type'], 'b')
+
+    def test_find_existing_by_remote_id(self):
+        ''' attempt to match a remote id to an object in the db '''
+        user = models.User.objects.create_user(
+            'mouse', 'mouse@mouse.mouse', 'mouseword', local=True)
+        user.remote_id = 'http://example.com/a/b'
+        user.save()
+
+        # uses a different remote id scheme
+        book = models.Edition.objects.create(
+            title='Test Edition', remote_id='http://book.com/book')
+        # this isn't really part of this test directly but it's helpful to state
+        self.assertEqual(book.origin_id, 'http://book.com/book')
+        self.assertNotEqual(book.remote_id, 'http://book.com/book')
+
+        # uses subclasses
+        models.Comment.objects.create(
+            user=user, content='test status', book=book, \
+            remote_id='https://comment.net')
+
+        result = find_existing_by_remote_id(models.User, 'hi')
+        self.assertIsNone(result)
+
+        result = find_existing_by_remote_id(
+            models.User, 'http://example.com/a/b')
+        self.assertEqual(result, user)
+
+        # test using origin id
+        result = find_existing_by_remote_id(
+            models.Edition, 'http://book.com/book')
+        self.assertEqual(result, book)
+
+        # test subclass match
+        result = find_existing_by_remote_id(
+            models.Status, 'https://comment.net')