test(lobby): lock issue-310 transition ownership boundary

lobby/tests.py

@@ -107,6 +107,30 @@ class LobbyGameplayExtractionTests(TestCase):
         self.assertNotIn("build_reveal_scoreboard_response", source)
         self.assertNotIn("build_scoreboard_phase_event", source)
 
+    def test_issue_310_transition_views_keep_gameplay_logic_out_of_lobby(self):
+        transition_sources = {
+            "reveal_scoreboard": inspect.getsource(inspect.unwrap(lobby_views.reveal_scoreboard)),
+            "start_next_round": inspect.getsource(inspect.unwrap(lobby_views.start_next_round)),
+            "finish_game": inspect.getsource(inspect.unwrap(lobby_views.finish_game)),
+        }
+
+        forbidden_snippets = (
+            "select_round_question(",
+            "reset_round_question_bootstrap_state(",
+            "build_start_next_round_response(",
+            "build_start_next_round_phase_event(",
+            "build_finish_game_response(",
+            "build_finish_game_phase_event(",
+            "build_reveal_scoreboard_response(",
+            "build_scoreboard_phase_event(",
+            "ScoreEvent.objects.filter(",
+            "Player.objects.filter(",
+        )
+
+        for view_name, source in transition_sources.items():
+            for snippet in forbidden_snippets:
+                self.assertNotIn(snippet, source, msg=f"{view_name} leaked gameplay snippet: {snippet}")
+
     def test_session_detail_view_source_stays_http_thin(self):
         source = inspect.getsource(inspect.unwrap(lobby_views.session_detail))