make-test-robust

Author: Darshan808

tests/test_formatters.py

@@ -62,6 +62,7 @@ def test_display_formatter_active_types_config():
     from traitlets.config import Config
 
     # Clear HistoryManager instances to bypass singleton limit before creating new shell
+    prev_instances = HistoryManager._instances.copy()
     HistoryManager._instances.clear()
 
     try:
@@ -73,8 +74,13 @@ def test_display_formatter_active_types_config():
         active_types = ip.display_formatter.active_types
         assert "text/plain" in active_types
         assert "image/png" in active_types
+
+        # Ensure only the expected types are active
+        assert set(active_types) == {"text/plain", "image/png"}
     finally:
+        # Clean up the new instance and restore previous state
         HistoryManager._instances.clear()
+        HistoryManager._instances.update(prev_instances)
 
 
 def test_pretty():