Add tests to show that the excess turns are discarded when creating the readable tracker

tests/shared/utils/test_llm.py

@@ -59,6 +59,49 @@ def test_tracker_as_readable_transcript_handles_tracker_with_events_and_max_turn
     assert tracker_as_readable_transcript(tracker, max_turns=1) == ("""AI: hi""")
 
 
+def test_tracker_as_readable_transcript_and_discard_excess_turns_with_default_max_turns(
+    domain: Domain,
+):
+    tracker = DialogueStateTracker(sender_id="test", slots=domain.slots)
+    tracker.update_with_events(
+        [
+            UserUttered("A0"),
+            BotUttered("B1"),
+            UserUttered("C2"),
+            BotUttered("D3"),
+            UserUttered("E4"),
+            BotUttered("F5"),
+            UserUttered("G6"),
+            BotUttered("H7"),
+            UserUttered("I8"),
+            BotUttered("J9"),
+            UserUttered("K10"),
+            BotUttered("L11"),
+            UserUttered("M12"),
+            BotUttered("N13"),
+            UserUttered("O14"),
+            BotUttered("P15"),
+            UserUttered("Q16"),
+            BotUttered("R17"),
+            UserUttered("S18"),
+            BotUttered("T19"),
+            UserUttered("U20"),
+            BotUttered("V21"),
+            UserUttered("W22"),
+            BotUttered("X23"),
+            UserUttered("Y24"),
+        ],
+        domain,
+    )
+    response = tracker_as_readable_transcript(tracker)
+    assert response == (
+        """AI: F5\nUSER: G6\nAI: H7\nUSER: I8\nAI: J9\nUSER: K10\nAI: L11\n"""
+        """USER: M12\nAI: N13\nUSER: O14\nAI: P15\nUSER: Q16\nAI: R17\nUSER: S18\n"""
+        """AI: T19\nUSER: U20\nAI: V21\nUSER: W22\nAI: X23\nUSER: Y24"""
+    )
+    assert response.count("\n") == 19
+
+
 def test_sanitize_message_for_prompt_handles_none():
     assert sanitize_message_for_prompt(None) == ""