Enhance output formatting in dump comparator (#21029)

test/registered/debug_utils/comparator/test_model_validation.py

@@ -345,26 +345,37 @@ class TestOutputRecordCategories:
 
     def test_error_record_category_is_errored(self) -> None:
         record = ComparisonErrorRecord(
-            name="t", exception_type="ValueError", traceback_str="..."
+            name="t",
+            exception_type="ValueError",
+            exception_message="bad",
+            traceback_str="...",
         )
         assert record.category == "errored"
 
     def test_error_record_json_roundtrip(self) -> None:
         record = ComparisonErrorRecord(
-            name="t", exception_type="ValueError", traceback_str="traceback..."
+            name="t",
+            exception_type="ValueError",
+            exception_message="bad",
+            traceback_str="traceback...",
         )
         json_str: str = record.model_dump_json()
         roundtripped = parse_record_json(json_str)
         assert isinstance(roundtripped, ComparisonErrorRecord)
         assert roundtripped.name == "t"
         assert roundtripped.exception_type == "ValueError"
+        assert roundtripped.exception_message == "bad"
 
     def test_error_record_text_format(self) -> None:
         record = ComparisonErrorRecord(
-            name="t", exception_type="RuntimeError", traceback_str="Traceback..."
+            name="t",
+            exception_type="RuntimeError",
+            exception_message="oops",
+            traceback_str="Traceback...",
         )
         text: str = record.to_text()
         assert "RuntimeError" in text
+        assert "oops" in text
         assert "Traceback" in text