Add tests

We add a series of tests that check whether device list sending works
across a variety of possible configurations.

tests/handlers/test_appservice.py

@@ -15,6 +15,8 @@
 from typing import Dict, Iterable, List, Optional
 from unittest.mock import Mock
 
+from parameterized import parameterized
+
 from twisted.internet import defer
 from twisted.test.proto_helpers import MemoryReactor
 
@@ -636,6 +638,115 @@ def _register_application_service(
         return appservice
 
 
+class ApplicationServicesHandlerDeviceListsTestCase(unittest.HomeserverTestCase):
+    """
+    Tests that the ApplicationServicesHandler sends device list updates to application
+    services correctly.
+    """
+
+    servlets = [
+        synapse.rest.admin.register_servlets_for_client_rest_resource,
+        login.register_servlets,
+        room.register_servlets,
+    ]
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        # Allow us to modify cached feature flags mid-test
+        self.as_handler = hs.get_application_service_handler()
+
+        # Mock ApplicationServiceApi's put_json, so we can verify the raw JSON that
+        # will be sent over the wire
+        self.put_json = simple_async_mock()
+        hs.get_application_service_api().put_json = self.put_json  # type: ignore[assignment]
+
+        # Mock out application services, and allow defining our own in tests
+        self._services: List[ApplicationService] = []
+        self.hs.get_datastores().main.get_app_services = Mock(
+            return_value=self._services
+        )
+
+    # Test across a variety of configuration values
+    @parameterized.expand(
+        [
+            (True, True, True),
+            (True, False, False),
+            (False, True, False),
+            (False, False, False),
+        ]
+    )
+    @unittest.override_config({"experimental_features": {"": False}})
+    def test_application_service_receives_device_list_updates(
+        self,
+        experimental_feature_enabled: bool,
+        as_supports_txn_extensions: bool,
+        as_should_receive_device_list_updates: bool,
+    ):
+        """
+        Tests that an application service receives notice of changed device
+        lists for a user, when a user changes their device lists.
+
+        Arguments above are populated by parameterized.
+
+        Args:
+            as_should_receive_device_list_updates: Whether we expect the AS to receive the
+                device list changes.
+            experimental_feature_enabled: Whether the "msc3202_transaction_extensions" experimental
+                feature is enabled. This feature must be enabled for device lists to ASs to work.
+            as_supports_txn_extensions: Whether the application service has explicitly registered
+                to receive information defined by MSC3202 - which includes device list changes.
+        """
+        # Change whether the experimental feature is enabled or disabled before making
+        # device list changes
+        self.as_handler._msc3202_transaction_extensions_enabled = (
+            experimental_feature_enabled
+        )
+
+        # Create an appservice that is interested in "local_user"
+        appservice = ApplicationService(
+            token=random_string(10),
+            hostname="example.com",
+            id=random_string(10),
+            sender="@as:example.com",
+            rate_limited=False,
+            namespaces={
+                ApplicationService.NS_USERS: [
+                    {
+                        "regex": "@local_user:.+",
+                        "exclusive": False,
+                    }
+                ],
+            },
+            supports_ephemeral=True,
+            msc3202_transaction_extensions=as_supports_txn_extensions,
+            # Must be set for Synapse to try pushing data to the AS
+            hs_token="abcde",
+            url="some_url",
+        )
+
+        # Register the application service
+        self._services.append(appservice)
+
+        # Register a user on the homeserver
+        self.local_user = self.register_user("local_user", "password")
+        self.local_user_token = self.login("local_user", "password")
+
+        if as_should_receive_device_list_updates:
+            # Ensure that the resulting JSON uses the unstable prefix and contains the
+            # expected users
+            self.put_json.assert_called_once()
+            json_body = self.put_json.call_args.kwargs["json_body"]
+
+            # Our application service should have received a device list update with
+            # "local_user" in the "changed" list
+            device_list_dict = json_body.get("org.matrix.msc3202.device_lists", {})
+            self.assertEqual([], device_list_dict["left"])
+            self.assertEqual([self.local_user], device_list_dict["changed"])
+
+        else:
+            # No device list changes should have been sent out
+            self.put_json.assert_not_called()
+
+
 class ApplicationServicesHandlerOtkCountsTestCase(unittest.HomeserverTestCase):
     # Argument indices for pulling out arguments from a `send_mock`.
     ARG_OTK_COUNTS = 4