fix: remove unsupported timestamp_ntz cast tests and fix date_format test

- Remove cast tests for TimestampNTZType to LongType (Spark doesn't support)
- Remove cast tests for numeric types and BinaryType to TimestampNTZType
  (Spark doesn't support these casts)
- Fix date_format timestamp_ntz test by using UTC timezone explicitly
  (Comet interprets timestamp_ntz as UTC during cast, which differs from
  Spark's session timezone behavior for non-UTC timezones)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: andygrove

spark/src/test/scala/org/apache/comet/CometCastSuite.scala

@@ -1038,10 +1038,6 @@ class CometCastSuite extends CometTestBase with AdaptiveSparkPlanHelper {
 
   // CAST from TimestampNTZType
 
-  test("cast TimestampNTZType to LongType") {
-    castTest(generateTimestampNTZs(), DataTypes.LongType)
-  }
-
   test("cast TimestampNTZType to StringType") {
     castTest(generateTimestampNTZs(), DataTypes.StringType)
   }
@@ -1055,46 +1051,8 @@ class CometCastSuite extends CometTestBase with AdaptiveSparkPlanHelper {
   }
 
   // CAST to TimestampNTZType
-
-  ignore("cast BooleanType to TimestampNTZType") {
-    // Spark does not support this cast
-    castTest(generateBools(), DataTypes.TimestampNTZType)
-  }
-
-  ignore("cast ByteType to TimestampNTZType") {
-    // Not yet implemented
-    castTest(generateBytes(), DataTypes.TimestampNTZType)
-  }
-
-  ignore("cast ShortType to TimestampNTZType") {
-    // Not yet implemented
-    castTest(generateShorts(), DataTypes.TimestampNTZType)
-  }
-
-  ignore("cast IntegerType to TimestampNTZType") {
-    // Not yet implemented
-    castTest(generateInts(), DataTypes.TimestampNTZType)
-  }
-
-  ignore("cast LongType to TimestampNTZType") {
-    // Not yet implemented
-    castTest(generateLongs(), DataTypes.TimestampNTZType)
-  }
-
-  ignore("cast FloatType to TimestampNTZType") {
-    // Not yet implemented
-    castTest(generateFloats(), DataTypes.TimestampNTZType)
-  }
-
-  ignore("cast DoubleType to TimestampNTZType") {
-    // Not yet implemented
-    castTest(generateDoubles(), DataTypes.TimestampNTZType)
-  }
-
-  ignore("cast DecimalType(10,2) to TimestampNTZType") {
-    // Not yet implemented
-    castTest(generateDecimalsPrecision10Scale2(), DataTypes.TimestampNTZType)
-  }
+  // Note: Spark does not support casting numeric types (Byte, Short, Int, Long, Float, Double,
+  // Decimal) or BinaryType to TimestampNTZType, so those tests are not included here.
 
   ignore("cast StringType to TimestampNTZType") {
     // Not yet implemented
@@ -1103,11 +1061,6 @@ class CometCastSuite extends CometTestBase with AdaptiveSparkPlanHelper {
       DataTypes.TimestampNTZType)
   }
 
-  ignore("cast BinaryType to TimestampNTZType") {
-    // Spark does not support this cast
-    castTest(generateBinary(), DataTypes.TimestampNTZType)
-  }
-
   ignore("cast DateType to TimestampNTZType") {
     // Not yet implemented
     castTest(generateDates(), DataTypes.TimestampNTZType)

spark/src/test/scala/org/apache/comet/CometTemporalExpressionSuite.scala

@@ -177,14 +177,20 @@ class CometTemporalExpressionSuite extends CometTestBase with AdaptiveSparkPlanH
   }
 
   test("date_format - timestamp_ntz input") {
-    val r = new Random(42)
-    val ntzSchema = StructType(Seq(StructField("ts_ntz", DataTypes.TimestampNTZType, true)))
-    val ntzDF = FuzzDataGenerator.generateDataFrame(r, spark, ntzSchema, 100, DataGenOptions())
-    ntzDF.createOrReplaceTempView("ntz_tbl")
-    val supportedFormats = CometDateFormat.supportedFormats.keys.toSeq.filterNot(_.contains("'"))
-    for (format <- supportedFormats) {
-      checkSparkAnswerAndOperator(
-        s"SELECT ts_ntz, date_format(ts_ntz, '$format') from ntz_tbl order by ts_ntz")
+    // Comet's date_format with timestamp_ntz is only compatible with UTC timezone because
+    // the cast from timestamp_ntz to timestamp interprets the value as UTC, not the session
+    // timezone. For non-UTC timezones, Comet falls back to Spark.
+    withSQLConf(SQLConf.SESSION_LOCAL_TIMEZONE.key -> "UTC") {
+      val r = new Random(42)
+      val ntzSchema = StructType(Seq(StructField("ts_ntz", DataTypes.TimestampNTZType, true)))
+      val ntzDF = FuzzDataGenerator.generateDataFrame(r, spark, ntzSchema, 100, DataGenOptions())
+      ntzDF.createOrReplaceTempView("ntz_tbl")
+      val supportedFormats =
+        CometDateFormat.supportedFormats.keys.toSeq.filterNot(_.contains("'"))
+      for (format <- supportedFormats) {
+        checkSparkAnswerAndOperator(
+          s"SELECT ts_ntz, date_format(ts_ntz, '$format') from ntz_tbl order by ts_ntz")
+      }
     }
   }