diff --git a/changelog.d/12348.misc b/changelog.d/12348.misc
new file mode 100644
index 0000000000..2bfeadb7f8
--- /dev/null
+++ b/changelog.d/12348.misc
@@ -0,0 +1 @@
+Move single-use methods out of `TestCase`.
diff --git a/tests/rest/client/test_account.py b/tests/rest/client/test_account.py
index 27946febff..e00b5c171c 100644
--- a/tests/rest/client/test_account.py
+++ b/tests/rest/client/test_account.py
@@ -89,6 +89,17 @@ class PasswordResetTestCase(unittest.HomeserverTestCase):
         self.store = hs.get_datastores().main
         self.submit_token_resource = PasswordResetSubmitTokenResource(hs)
 
+    def attempt_wrong_password_login(self, username: str, password: str) -> None:
+        """Attempts to login as the user with the given password, asserting
+        that the attempt *fails*.
+        """
+        body = {"type": "m.login.password", "user": username, "password": password}
+
+        channel = self.make_request(
+            "POST", "/_matrix/client/r0/login", json.dumps(body).encode("utf8")
+        )
+        self.assertEqual(channel.code, 403, channel.result)
+
     def test_basic_password_reset(self) -> None:
         """Test basic password reset flow"""
         old_password = "monkey"
diff --git a/tests/storage/test_cleanup_extrems.py b/tests/storage/test_cleanup_extrems.py
index ce89c96912..fe91c3fed8 100644
--- a/tests/storage/test_cleanup_extrems.py
+++ b/tests/storage/test_cleanup_extrems.py
@@ -68,6 +68,22 @@ class CleanupExtremBackgroundUpdateStoreTestCase(HomeserverTestCase):
 
         self.wait_for_background_updates()
 
+    def add_extremity(self, room_id: str, event_id: str) -> None:
+        """
+        Add the given event as an extremity to the room.
+        """
+        self.get_success(
+            self.hs.get_datastores().main.db_pool.simple_insert(
+                table="event_forward_extremities",
+                values={"room_id": room_id, "event_id": event_id},
+                desc="test_add_extremity",
+            )
+        )
+
+        self.hs.get_datastores().main.get_latest_event_ids_in_room.invalidate(
+            (room_id,)
+        )
+
     def test_soft_failed_extremities_handled_correctly(self):
         """Test that extremities are correctly calculated in the presence of
         soft failed events.
diff --git a/tests/unittest.py b/tests/unittest.py
index 326895f4c9..cbe215ee83 100644
--- a/tests/unittest.py
+++ b/tests/unittest.py
@@ -717,33 +717,6 @@ class HomeserverTestCase(TestCase):
 
         return event.event_id
 
-    def add_extremity(self, room_id, event_id):
-        """
-        Add the given event as an extremity to the room.
-        """
-        self.get_success(
-            self.hs.get_datastores().main.db_pool.simple_insert(
-                table="event_forward_extremities",
-                values={"room_id": room_id, "event_id": event_id},
-                desc="test_add_extremity",
-            )
-        )
-
-        self.hs.get_datastores().main.get_latest_event_ids_in_room.invalidate(
-            (room_id,)
-        )
-
-    def attempt_wrong_password_login(self, username, password):
-        """Attempts to login as the user with the given password, asserting
-        that the attempt *fails*.
-        """
-        body = {"type": "m.login.password", "user": username, "password": password}
-
-        channel = self.make_request(
-            "POST", "/_matrix/client/r0/login", json.dumps(body).encode("utf8")
-        )
-        self.assertEqual(channel.code, 403, channel.result)
-
     def inject_room_member(self, room: str, user: str, membership: Membership) -> None:
         """
         Inject a membership event into a room.