diff --git a/changelog.d/14568.misc b/changelog.d/14568.misc
new file mode 100644
index 000000000..99973de1c
--- /dev/null
+++ b/changelog.d/14568.misc
@@ -0,0 +1 @@
+Modernize unit tests configuration related to workers.
diff --git a/tests/events/test_presence_router.py b/tests/events/test_presence_router.py
index 685a9a6d5..b703e4472 100644
--- a/tests/events/test_presence_router.py
+++ b/tests/events/test_presence_router.py
@@ -126,6 +126,13 @@ class PresenceRouterTestModule:
 
 
 class PresenceRouterTestCase(FederatingHomeserverTestCase):
+    """
+    Test cases using a custom PresenceRouter
+
+    By default in test cases, federation sending is disabled. This class re-enables it
+    for the main process by setting `federation_sender_instances` to None.
+    """
+
     servlets = [
         admin.register_servlets,
         login.register_servlets,
@@ -150,6 +157,11 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
         self.sync_handler = self.hs.get_sync_handler()
         self.module_api = homeserver.get_module_api()
 
+    def default_config(self) -> JsonDict:
+        config = super().default_config()
+        config["federation_sender_instances"] = None
+        return config
+
     @override_config(
         {
             "presence": {
@@ -162,7 +174,6 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
                     },
                 }
             },
-            "send_federation": True,
         }
     )
     def test_receiving_all_presence_legacy(self):
@@ -180,7 +191,6 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
                     },
                 },
             ],
-            "send_federation": True,
         }
     )
     def test_receiving_all_presence(self):
@@ -290,7 +300,6 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
                     },
                 }
             },
-            "send_federation": True,
         }
     )
     def test_send_local_online_presence_to_with_module_legacy(self):
@@ -310,7 +319,6 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
                     },
                 },
             ],
-            "send_federation": True,
         }
     )
     def test_send_local_online_presence_to_with_module(self):
diff --git a/tests/federation/test_federation_catch_up.py b/tests/federation/test_federation_catch_up.py
index 2873b4d43..b8fee7289 100644
--- a/tests/federation/test_federation_catch_up.py
+++ b/tests/federation/test_federation_catch_up.py
@@ -7,13 +7,21 @@ from synapse.federation.sender import PerDestinationQueue, TransactionManager
 from synapse.federation.units import Edu
 from synapse.rest import admin
 from synapse.rest.client import login, room
+from synapse.types import JsonDict
 from synapse.util.retryutils import NotRetryingDestination
 
 from tests.test_utils import event_injection, make_awaitable
-from tests.unittest import FederatingHomeserverTestCase, override_config
+from tests.unittest import FederatingHomeserverTestCase
 
 
 class FederationCatchUpTestCases(FederatingHomeserverTestCase):
+    """
+    Tests cases of catching up over federation.
+
+    By default for test cases federation sending is disabled. This Test class has it
+    re-enabled for the main process.
+    """
+
     servlets = [
         admin.register_servlets,
         room.register_servlets,
@@ -42,6 +50,11 @@ class FederationCatchUpTestCases(FederatingHomeserverTestCase):
             self.record_transaction
         )
 
+    def default_config(self) -> JsonDict:
+        config = super().default_config()
+        config["federation_sender_instances"] = None
+        return config
+
     async def record_transaction(self, txn, json_cb):
         if self.is_online:
             data = json_cb()
@@ -79,7 +92,6 @@ class FederationCatchUpTestCases(FederatingHomeserverTestCase):
         )[0]
         return {"event_id": event_id, "stream_ordering": stream_ordering}
 
-    @override_config({"send_federation": True})
     def test_catch_up_destination_rooms_tracking(self):
         """
         Tests that we populate the `destination_rooms` table as needed.
@@ -105,7 +117,6 @@ class FederationCatchUpTestCases(FederatingHomeserverTestCase):
         self.assertEqual(row_2["event_id"], event_id_2)
         self.assertEqual(row_1["stream_ordering"], row_2["stream_ordering"] - 1)
 
-    @override_config({"send_federation": True})
     def test_catch_up_last_successful_stream_ordering_tracking(self):
         """
         Tests that we populate the `destination_rooms` table as needed.
@@ -163,7 +174,6 @@ class FederationCatchUpTestCases(FederatingHomeserverTestCase):
             "Send succeeded but not marked as last_successful_stream_ordering",
         )
 
-    @override_config({"send_federation": True})  # critical to federate
     def test_catch_up_from_blank_state(self):
         """
         Runs an overall test of federation catch-up from scratch.
@@ -260,7 +270,6 @@ class FederationCatchUpTestCases(FederatingHomeserverTestCase):
 
         return per_dest_queue, results_list
 
-    @override_config({"send_federation": True})
     def test_catch_up_loop(self):
         """
         Tests the behaviour of _catch_up_transmission_loop.
@@ -325,7 +334,6 @@ class FederationCatchUpTestCases(FederatingHomeserverTestCase):
             event_5.internal_metadata.stream_ordering,
         )
 
-    @override_config({"send_federation": True})
     def test_catch_up_on_synapse_startup(self):
         """
         Tests the behaviour of get_catch_up_outstanding_destinations and
@@ -424,7 +432,6 @@ class FederationCatchUpTestCases(FederatingHomeserverTestCase):
         # - all destinations are woken exactly once; they appear once in woken.
         self.assertCountEqual(woken, server_names[:-1])
 
-    @override_config({"send_federation": True})
     def test_not_latest_event(self):
         """Test that we send the latest event in the room even if its not ours."""
 
diff --git a/tests/federation/test_federation_sender.py b/tests/federation/test_federation_sender.py
index cbc99d30b..8692d8190 100644
--- a/tests/federation/test_federation_sender.py
+++ b/tests/federation/test_federation_sender.py
@@ -25,10 +25,17 @@ from synapse.rest.client import login
 from synapse.types import JsonDict, ReadReceipt
 
 from tests.test_utils import make_awaitable
-from tests.unittest import HomeserverTestCase, override_config
+from tests.unittest import HomeserverTestCase
 
 
 class FederationSenderReceiptsTestCases(HomeserverTestCase):
+    """
+    Test federation sending to update receipts.
+
+    By default for test cases federation sending is disabled. This Test class has it
+    re-enabled for the main process.
+    """
+
     def make_homeserver(self, reactor, clock):
         hs = self.setup_test_homeserver(
             federation_transport_client=Mock(spec=["send_transaction"]),
@@ -44,7 +51,11 @@ class FederationSenderReceiptsTestCases(HomeserverTestCase):
 
         return hs
 
-    @override_config({"send_federation": True})
+    def default_config(self) -> JsonDict:
+        config = super().default_config()
+        config["federation_sender_instances"] = None
+        return config
+
     def test_send_receipts(self):
         mock_send_transaction = (
             self.hs.get_federation_transport_client().send_transaction
@@ -87,7 +98,6 @@ class FederationSenderReceiptsTestCases(HomeserverTestCase):
             ],
         )
 
-    @override_config({"send_federation": True})
     def test_send_receipts_thread(self):
         mock_send_transaction = (
             self.hs.get_federation_transport_client().send_transaction
@@ -164,7 +174,6 @@ class FederationSenderReceiptsTestCases(HomeserverTestCase):
             ],
         )
 
-    @override_config({"send_federation": True})
     def test_send_receipts_with_backoff(self):
         """Send two receipts in quick succession; the second should be flushed, but
         only after 20ms"""
@@ -251,6 +260,13 @@ class FederationSenderReceiptsTestCases(HomeserverTestCase):
 
 
 class FederationSenderDevicesTestCases(HomeserverTestCase):
+    """
+    Test federation sending to update devices.
+
+    By default for test cases federation sending is disabled. This Test class has it
+    re-enabled for the main process.
+    """
+
     servlets = [
         admin.register_servlets,
         login.register_servlets,
@@ -265,7 +281,8 @@ class FederationSenderDevicesTestCases(HomeserverTestCase):
 
     def default_config(self):
         c = super().default_config()
-        c["send_federation"] = True
+        # Enable federation sending on the main process.
+        c["federation_sender_instances"] = None
         return c
 
     def prepare(self, reactor, clock, hs):
diff --git a/tests/handlers/test_presence.py b/tests/handlers/test_presence.py
index c5981ff96..584e7b897 100644
--- a/tests/handlers/test_presence.py
+++ b/tests/handlers/test_presence.py
@@ -992,7 +992,8 @@ class PresenceJoinTestCase(unittest.HomeserverTestCase):
 
     def default_config(self):
         config = super().default_config()
-        config["send_federation"] = True
+        # Enable federation sending on the main process.
+        config["federation_sender_instances"] = None
         return config
 
     def prepare(self, reactor, clock, hs):
diff --git a/tests/handlers/test_typing.py b/tests/handlers/test_typing.py
index 9c821b304..efbb5a8db 100644
--- a/tests/handlers/test_typing.py
+++ b/tests/handlers/test_typing.py
@@ -200,7 +200,8 @@ class TypingNotificationsTestCase(unittest.HomeserverTestCase):
             ],
         )
 
-    @override_config({"send_federation": True})
+    # Enable federation sending on the main process.
+    @override_config({"federation_sender_instances": None})
     def test_started_typing_remote_send(self) -> None:
         self.room_members = [U_APPLE, U_ONION]
 
@@ -305,7 +306,8 @@ class TypingNotificationsTestCase(unittest.HomeserverTestCase):
         self.assertEqual(events[0], [])
         self.assertEqual(events[1], 0)
 
-    @override_config({"send_federation": True})
+    # Enable federation sending on the main process.
+    @override_config({"federation_sender_instances": None})
     def test_stopped_typing(self) -> None:
         self.room_members = [U_APPLE, U_BANANA, U_ONION]
 
diff --git a/tests/handlers/test_user_directory.py b/tests/handlers/test_user_directory.py
index 9e39cd97e..75fc5a17a 100644
--- a/tests/handlers/test_user_directory.py
+++ b/tests/handlers/test_user_directory.py
@@ -56,7 +56,8 @@ class UserDirectoryTestCase(unittest.HomeserverTestCase):
 
     def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
         config = self.default_config()
-        config["update_user_directory"] = True
+        # Re-enables updating the user directory, as that function is needed below.
+        config["update_user_directory_from_worker"] = None
 
         self.appservice = ApplicationService(
             token="i_am_an_app_service",
@@ -1045,7 +1046,9 @@ class TestUserDirSearchDisabled(unittest.HomeserverTestCase):
 
     def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
         config = self.default_config()
-        config["update_user_directory"] = True
+        # Re-enables updating the user directory, as that function is needed below. It
+        # will be force disabled later
+        config["update_user_directory_from_worker"] = None
         hs = self.setup_test_homeserver(config=config)
 
         self.config = hs.config
diff --git a/tests/module_api/test_api.py b/tests/module_api/test_api.py
index 058ca57e5..b0f3f4374 100644
--- a/tests/module_api/test_api.py
+++ b/tests/module_api/test_api.py
@@ -336,7 +336,8 @@ class ModuleApiTestCase(HomeserverTestCase):
         # Test sending local online presence to users from the main process
         _test_sending_local_online_presence_to_local_user(self, test_with_workers=False)
 
-    @override_config({"send_federation": True})
+    # Enable federation sending on the main process.
+    @override_config({"federation_sender_instances": None})
     def test_send_local_online_presence_to_federation(self):
         """Tests that send_local_presence_to_users sends local online presence to remote users."""
         # Create a user who will send presence updates
diff --git a/tests/push/test_email.py b/tests/push/test_email.py
index fd14568f5..57b2f0536 100644
--- a/tests/push/test_email.py
+++ b/tests/push/test_email.py
@@ -66,7 +66,6 @@ class EmailPusherTests(HomeserverTestCase):
             "riot_base_url": None,
         }
         config["public_baseurl"] = "http://aaa"
-        config["start_pushers"] = True
 
         hs = self.setup_test_homeserver(config=config)
 
diff --git a/tests/push/test_http.py b/tests/push/test_http.py
index b383b8401..afaafe79a 100644
--- a/tests/push/test_http.py
+++ b/tests/push/test_http.py
@@ -11,7 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from typing import Any, Dict, List, Optional, Tuple
+from typing import List, Optional, Tuple
 from unittest.mock import Mock
 
 from twisted.internet.defer import Deferred
@@ -41,11 +41,6 @@ class HTTPPusherTests(HomeserverTestCase):
     user_id = True
     hijack_auth = False
 
-    def default_config(self) -> Dict[str, Any]:
-        config = super().default_config()
-        config["start_pushers"] = True
-        return config
-
     def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
         self.push_attempts: List[Tuple[Deferred, str, dict]] = []
 
diff --git a/tests/replication/_base.py b/tests/replication/_base.py
index 3029a16dd..6a7174b33 100644
--- a/tests/replication/_base.py
+++ b/tests/replication/_base.py
@@ -307,7 +307,7 @@ class BaseMultiWorkerStreamTestCase(unittest.HomeserverTestCase):
         stream to the master HS.
 
         Args:
-            worker_app: Type of worker, e.g. `synapse.app.federation_sender`.
+            worker_app: Type of worker, e.g. `synapse.app.generic_worker`.
             extra_config: Any extra config to use for this instances.
             **kwargs: Options that get passed to `self.setup_test_homeserver`,
                 useful to e.g. pass some mocks for things like `federation_http_client`
diff --git a/tests/replication/tcp/streams/test_federation.py b/tests/replication/tcp/streams/test_federation.py
index ffec06a0d..bcb82c9c8 100644
--- a/tests/replication/tcp/streams/test_federation.py
+++ b/tests/replication/tcp/streams/test_federation.py
@@ -22,9 +22,8 @@ class FederationStreamTestCase(BaseStreamTestCase):
     def _get_worker_hs_config(self) -> dict:
         # enable federation sending on the worker
         config = super()._get_worker_hs_config()
-        # TODO: make it so we don't need both of these
-        config["send_federation"] = False
-        config["worker_app"] = "synapse.app.federation_sender"
+        config["worker_name"] = "federation_sender1"
+        config["federation_sender_instances"] = ["federation_sender1"]
         return config
 
     def test_catchup(self):
diff --git a/tests/replication/test_auth.py b/tests/replication/test_auth.py
index 43a16bb14..5d7a89e0c 100644
--- a/tests/replication/test_auth.py
+++ b/tests/replication/test_auth.py
@@ -38,7 +38,7 @@ class WorkerAuthenticationTestCase(BaseMultiWorkerStreamTestCase):
 
     def _get_worker_hs_config(self) -> dict:
         config = self.default_config()
-        config["worker_app"] = "synapse.app.client_reader"
+        config["worker_app"] = "synapse.app.generic_worker"
         config["worker_replication_host"] = "testserv"
         config["worker_replication_http_port"] = "8765"
 
@@ -53,7 +53,7 @@ class WorkerAuthenticationTestCase(BaseMultiWorkerStreamTestCase):
         4. Return the final request.
 
         """
-        worker_hs = self.make_worker_hs("synapse.app.client_reader")
+        worker_hs = self.make_worker_hs("synapse.app.generic_worker")
         site = self._hs_to_site[worker_hs]
 
         channel_1 = make_request(
diff --git a/tests/replication/test_client_reader_shard.py b/tests/replication/test_client_reader_shard.py
index 995097d72..eb5b37653 100644
--- a/tests/replication/test_client_reader_shard.py
+++ b/tests/replication/test_client_reader_shard.py
@@ -22,20 +22,20 @@ logger = logging.getLogger(__name__)
 
 
 class ClientReaderTestCase(BaseMultiWorkerStreamTestCase):
-    """Test using one or more client readers for registration."""
+    """Test using one or more generic workers for registration."""
 
     servlets = [register.register_servlets]
 
     def _get_worker_hs_config(self) -> dict:
         config = self.default_config()
-        config["worker_app"] = "synapse.app.client_reader"
+        config["worker_app"] = "synapse.app.generic_worker"
         config["worker_replication_host"] = "testserv"
         config["worker_replication_http_port"] = "8765"
         return config
 
     def test_register_single_worker(self):
-        """Test that registration works when using a single client reader worker."""
-        worker_hs = self.make_worker_hs("synapse.app.client_reader")
+        """Test that registration works when using a single generic worker."""
+        worker_hs = self.make_worker_hs("synapse.app.generic_worker")
         site = self._hs_to_site[worker_hs]
 
         channel_1 = make_request(
@@ -64,9 +64,9 @@ class ClientReaderTestCase(BaseMultiWorkerStreamTestCase):
         self.assertEqual(channel_2.json_body["user_id"], "@user:test")
 
     def test_register_multi_worker(self):
-        """Test that registration works when using multiple client reader workers."""
-        worker_hs_1 = self.make_worker_hs("synapse.app.client_reader")
-        worker_hs_2 = self.make_worker_hs("synapse.app.client_reader")
+        """Test that registration works when using multiple generic workers."""
+        worker_hs_1 = self.make_worker_hs("synapse.app.generic_worker")
+        worker_hs_2 = self.make_worker_hs("synapse.app.generic_worker")
 
         site_1 = self._hs_to_site[worker_hs_1]
         channel_1 = make_request(
diff --git a/tests/replication/test_federation_ack.py b/tests/replication/test_federation_ack.py
index 26b8bd512..63b1dd40b 100644
--- a/tests/replication/test_federation_ack.py
+++ b/tests/replication/test_federation_ack.py
@@ -25,8 +25,9 @@ from tests.unittest import HomeserverTestCase
 class FederationAckTestCase(HomeserverTestCase):
     def default_config(self) -> dict:
         config = super().default_config()
-        config["worker_app"] = "synapse.app.federation_sender"
-        config["send_federation"] = False
+        config["worker_app"] = "synapse.app.generic_worker"
+        config["worker_name"] = "federation_sender1"
+        config["federation_sender_instances"] = ["federation_sender1"]
         return config
 
     def make_homeserver(self, reactor, clock):
diff --git a/tests/replication/test_federation_sender_shard.py b/tests/replication/test_federation_sender_shard.py
index 6104a55aa..c28073b8f 100644
--- a/tests/replication/test_federation_sender_shard.py
+++ b/tests/replication/test_federation_sender_shard.py
@@ -27,17 +27,19 @@ logger = logging.getLogger(__name__)
 
 
 class FederationSenderTestCase(BaseMultiWorkerStreamTestCase):
+    """
+    Various tests for federation sending on workers.
+
+    Federation sending is disabled by default, it will be enabled in each test by
+    updating 'federation_sender_instances'.
+    """
+
     servlets = [
         login.register_servlets,
         register_servlets_for_client_rest_resource,
         room.register_servlets,
     ]
 
-    def default_config(self):
-        conf = super().default_config()
-        conf["send_federation"] = False
-        return conf
-
     def test_send_event_single_sender(self):
         """Test that using a single federation sender worker correctly sends a
         new event.
@@ -46,8 +48,11 @@ class FederationSenderTestCase(BaseMultiWorkerStreamTestCase):
         mock_client.put_json.return_value = make_awaitable({})
 
         self.make_worker_hs(
-            "synapse.app.federation_sender",
-            {"send_federation": False},
+            "synapse.app.generic_worker",
+            {
+                "worker_name": "federation_sender1",
+                "federation_sender_instances": ["federation_sender1"],
+            },
             federation_http_client=mock_client,
         )
 
@@ -73,11 +78,13 @@ class FederationSenderTestCase(BaseMultiWorkerStreamTestCase):
         mock_client1 = Mock(spec=["put_json"])
         mock_client1.put_json.return_value = make_awaitable({})
         self.make_worker_hs(
-            "synapse.app.federation_sender",
+            "synapse.app.generic_worker",
             {
-                "send_federation": True,
-                "worker_name": "sender1",
-                "federation_sender_instances": ["sender1", "sender2"],
+                "worker_name": "federation_sender1",
+                "federation_sender_instances": [
+                    "federation_sender1",
+                    "federation_sender2",
+                ],
             },
             federation_http_client=mock_client1,
         )
@@ -85,11 +92,13 @@ class FederationSenderTestCase(BaseMultiWorkerStreamTestCase):
         mock_client2 = Mock(spec=["put_json"])
         mock_client2.put_json.return_value = make_awaitable({})
         self.make_worker_hs(
-            "synapse.app.federation_sender",
+            "synapse.app.generic_worker",
             {
-                "send_federation": True,
-                "worker_name": "sender2",
-                "federation_sender_instances": ["sender1", "sender2"],
+                "worker_name": "federation_sender2",
+                "federation_sender_instances": [
+                    "federation_sender1",
+                    "federation_sender2",
+                ],
             },
             federation_http_client=mock_client2,
         )
@@ -136,11 +145,13 @@ class FederationSenderTestCase(BaseMultiWorkerStreamTestCase):
         mock_client1 = Mock(spec=["put_json"])
         mock_client1.put_json.return_value = make_awaitable({})
         self.make_worker_hs(
-            "synapse.app.federation_sender",
+            "synapse.app.generic_worker",
             {
-                "send_federation": True,
-                "worker_name": "sender1",
-                "federation_sender_instances": ["sender1", "sender2"],
+                "worker_name": "federation_sender1",
+                "federation_sender_instances": [
+                    "federation_sender1",
+                    "federation_sender2",
+                ],
             },
             federation_http_client=mock_client1,
         )
@@ -148,11 +159,13 @@ class FederationSenderTestCase(BaseMultiWorkerStreamTestCase):
         mock_client2 = Mock(spec=["put_json"])
         mock_client2.put_json.return_value = make_awaitable({})
         self.make_worker_hs(
-            "synapse.app.federation_sender",
+            "synapse.app.generic_worker",
             {
-                "send_federation": True,
-                "worker_name": "sender2",
-                "federation_sender_instances": ["sender1", "sender2"],
+                "worker_name": "federation_sender2",
+                "federation_sender_instances": [
+                    "federation_sender1",
+                    "federation_sender2",
+                ],
             },
             federation_http_client=mock_client2,
         )
diff --git a/tests/replication/test_pusher_shard.py b/tests/replication/test_pusher_shard.py
index 59fea93e4..ca18ad655 100644
--- a/tests/replication/test_pusher_shard.py
+++ b/tests/replication/test_pusher_shard.py
@@ -38,11 +38,6 @@ class PusherShardTestCase(BaseMultiWorkerStreamTestCase):
         self.other_user_id = self.register_user("otheruser", "pass")
         self.other_access_token = self.login("otheruser", "pass")
 
-    def default_config(self):
-        conf = super().default_config()
-        conf["start_pushers"] = False
-        return conf
-
     def _create_pusher_and_send_msg(self, localpart):
         # Create a user that will get push notifications
         user_id = self.register_user(localpart, "pass")
@@ -92,8 +87,8 @@ class PusherShardTestCase(BaseMultiWorkerStreamTestCase):
         )
 
         self.make_worker_hs(
-            "synapse.app.pusher",
-            {"start_pushers": False},
+            "synapse.app.generic_worker",
+            {"worker_name": "pusher1", "pusher_instances": ["pusher1"]},
             proxied_blacklisted_http_client=http_client_mock,
         )
 
@@ -122,9 +117,8 @@ class PusherShardTestCase(BaseMultiWorkerStreamTestCase):
         )
 
         self.make_worker_hs(
-            "synapse.app.pusher",
+            "synapse.app.generic_worker",
             {
-                "start_pushers": True,
                 "worker_name": "pusher1",
                 "pusher_instances": ["pusher1", "pusher2"],
             },
@@ -137,9 +131,8 @@ class PusherShardTestCase(BaseMultiWorkerStreamTestCase):
         )
 
         self.make_worker_hs(
-            "synapse.app.pusher",
+            "synapse.app.generic_worker",
             {
-                "start_pushers": True,
                 "worker_name": "pusher2",
                 "pusher_instances": ["pusher1", "pusher2"],
             },
diff --git a/tests/utils.py b/tests/utils.py
index 045a8b5fa..d76bf9716 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -125,7 +125,8 @@ def default_config(
     """
     config_dict = {
         "server_name": name,
-        "send_federation": False,
+        # Setting this to an empty list turns off federation sending.
+        "federation_sender_instances": [],
         "media_store_path": "media",
         # the test signing key is just an arbitrary ed25519 key to keep the config
         # parser happy
@@ -183,8 +184,9 @@ def default_config(
         # rooms will fail.
         "default_room_version": DEFAULT_ROOM_VERSION,
         # disable user directory updates, because they get done in the
-        # background, which upsets the test runner.
-        "update_user_directory": False,
+        # background, which upsets the test runner. Setting this to an
+        # (obviously) fake worker name disables updating the user directory.
+        "update_user_directory_from_worker": "does_not_exist_worker_name",
         "caches": {"global_factor": 1, "sync_response_cache_duration": 0},
         "listeners": [{"port": 0, "type": "http"}],
     }