Ensure that the whole test state has been consumed

Author: blast-hardcheese

tests/v2/fixtures.py

@@ -198,6 +198,14 @@ async def uri_and_metadata_factory() -> UriAndMetadata[None]:
 
     await driver_task
 
+    assert len(expected) == 0, "Unconsumed messages from 'expected'"
+    assert messages_to_client_channel.qsize() == 0, (
+        "Dangling messages the client has not consumed"
+    )
+    assert messages_from_client_channel.qsize() == 0, (
+        "Dangling messages the processor has not consumed"
+    )
+
     messages_to_client_channel.close()
     messages_from_client_channel.close()