Rename test and update assertions for clarity

Rename the test from `test_cast_to_extension_type` to
`test_cast_preserves_extension_metadata` to better reflect its
purpose. Replace the arrow.uuid fixture with a neutral extension
name "datafusion.test.int64_extension". Update the assertion to
check for the new extension name, ensuring that the test remains
focused on verifying that cast lowering preserves target field
metadata while surfacing extension metadata in the TryCast error
path.

Author: kosiew

datafusion/physical-expr/src/planner.rs

@@ -467,11 +467,17 @@ mod tests {
     }
 
     #[test]
-    fn test_cast_to_extension_type() -> Result<()> {
-        let extension_field_type =
-            Arc::new(DataType::Int64.into_nullable_field().with_metadata(
-                [("ARROW:extension:name".to_string(), "arrow.uuid".to_string())].into(),
-            ));
+    fn test_cast_preserves_extension_metadata() -> Result<()> {
+        let extension_name = "datafusion.test.int64_extension";
+        let extension_field_type = Arc::new(
+            DataType::Int64.into_nullable_field().with_metadata(
+                [(
+                    "ARROW:extension:name".to_string(),
+                    extension_name.to_string(),
+                )]
+                .into(),
+            ),
+        );
         let expr = col("value");
         let schema = Schema::new(vec![Field::new("value", DataType::Int32, false)]);
         let df_schema = DFSchema::try_from(schema.clone())?;
@@ -494,7 +500,7 @@ mod tests {
         let err =
             create_physical_expr(&try_cast_expr, &df_schema, &ExecutionProps::new())
                 .unwrap_err();
-        assert!(err.message().contains("arrow.uuid"));
+        assert!(err.message().contains(extension_name));
 
         Ok(())
     }