Increase platform abstraction cohesion

core/tests/test_transport_capabilities.py

@@ -1,5 +1,7 @@
+from asgiref.sync import async_to_sync
 from django.test import SimpleTestCase
 
+from core.clients import transport
 from core.transports.capabilities import capability_snapshot, supports, unsupported_reason
 
 
@@ -15,3 +17,11 @@ class TransportCapabilitiesTests(SimpleTestCase):
         snapshot = capability_snapshot()
         self.assertIn("schema_version", snapshot)
         self.assertIn("services", snapshot)
+
+    def test_transport_send_fails_fast_when_unsupported(self):
+        result = async_to_sync(transport.send_message_raw)(
+            "xmpp",
+            "person@example.com",
+            text="hello",
+        )
+        self.assertFalse(result)