Add tests to verify forward compatibility for unknown session event types

python/test_event_forward_compatibility.py

@@ -0,0 +1,64 @@
+"""
+Test that unknown event types are handled gracefully for forward compatibility.
+
+This test verifies that:
+1. The session.usage_info event type is recognized
+2. Unknown future event types map to UNKNOWN enum value
+3. Real parsing errors (malformed data) are NOT suppressed and surface for visibility
+"""
+
+from datetime import datetime
+from uuid import uuid4
+
+import pytest
+
+from copilot.generated.session_events import SessionEventType, session_event_from_dict
+
+
+class TestEventForwardCompatibility:
+    """Test forward compatibility for unknown event types."""
+
+    def test_session_usage_info_is_recognized(self):
+        """The session.usage_info event type should be in the enum."""
+        assert SessionEventType.SESSION_USAGE_INFO.value == "session.usage_info"
+
+    def test_unknown_event_type_maps_to_unknown(self):
+        """Unknown event types should map to UNKNOWN enum value for forward compatibility."""
+        unknown_event = {
+            "id": str(uuid4()),
+            "timestamp": datetime.now().isoformat(),
+            "parentId": None,
+            "type": "session.future_feature_from_server",
+            "data": {},
+        }
+
+        event = session_event_from_dict(unknown_event)
+        assert event.type == SessionEventType.UNKNOWN, f"Expected UNKNOWN, got {event.type}"
+
+    def test_malformed_uuid_raises_error(self):
+        """Malformed UUIDs should raise ValueError for visibility, not be suppressed."""
+        malformed_event = {
+            "id": "not-a-valid-uuid",
+            "timestamp": datetime.now().isoformat(),
+            "parentId": None,
+            "type": "session.start",
+            "data": {},
+        }
+
+        # This should raise an error and NOT be silently suppressed
+        with pytest.raises(ValueError):
+            session_event_from_dict(malformed_event)
+
+    def test_malformed_timestamp_raises_error(self):
+        """Malformed timestamps should raise an error for visibility."""
+        malformed_event = {
+            "id": str(uuid4()),
+            "timestamp": "not-a-valid-timestamp",
+            "parentId": None,
+            "type": "session.start",
+            "data": {},
+        }
+
+        # This should raise an error and NOT be silently suppressed
+        with pytest.raises((ValueError, TypeError)):
+            session_event_from_dict(malformed_event)