Add required test suite and websocket fixes

tests/test_reconnect.py

@@ -1,2 +1,22 @@
-def test_placeholder_reconnect():
-    assert True
+from conftest import create_session, join_student
+
+
+def test_reconnect_replays_existing_submit_ack(client, sample_pool):
+    sid = create_session(client, sample_pool)
+    join_student(client, sid, "s1", "Student One")
+    rooms = client.app.state.rooms
+    client.portal.call(rooms.open_question, sid, 0, 2)
+
+    with client.websocket_connect(f"/ws/student/{sid}") as ws:
+        assert ws.receive_json()["type"] == "state"
+        assert ws.receive_json()["type"] == "question_open"
+        ws.send_json({"type": "submit", "question_idx": 0, "answer": "B"})
+        ack = ws.receive_json()
+        assert ack["type"] == "submit_ack"
+
+    with client.websocket_connect(f"/ws/student/{sid}") as ws:
+        assert ws.receive_json()["type"] == "state"
+        assert ws.receive_json()["type"] == "question_open"
+        replay = ws.receive_json()
+        assert replay["type"] == "submit_ack"
+        assert replay["score"] == ack["score"]