diff --git a/spark/src/test/resources/sql-tests/expressions/string/left.sql b/spark/src/test/resources/sql-tests/expressions/string/left.sql
index 4605622e8b..31372f0a42 100644
--- a/spark/src/test/resources/sql-tests/expressions/string/left.sql
+++ b/spark/src/test/resources/sql-tests/expressions/string/left.sql
@@ -30,6 +30,17 @@ SELECT left(s, n) FROM test_str_left
 query
 SELECT left(s, 3) FROM test_str_left
 
+-- column + literal: edge cases
+query
+SELECT left(s, 0) FROM test_str_left
+
+query
+SELECT left(s, -1) FROM test_str_left
+
+query
+-- n exceeds length of 'hello' (5 chars)
+SELECT left(s, 10) FROM test_str_left
+
 -- literal + column
 query expect_fallback(Substring pos and len must be literals)
 SELECT left('hello', n) FROM test_str_left
@@ -37,3 +48,19 @@ SELECT left('hello', n) FROM test_str_left
 -- literal + literal
 query ignore(https://github.com/apache/datafusion-comet/issues/3337)
 SELECT left('hello', 3), left('hello', 0), left('hello', -1), left('', 3), left(NULL, 3)
+
+-- unicode
+statement
+CREATE TABLE test_str_left_unicode(s string) USING parquet
+
+statement
+INSERT INTO test_str_left_unicode VALUES ('café'), ('hello世界'), ('😀emoji'), ('తెలుగు'), (NULL)
+
+query
+SELECT s, left(s, 2) FROM test_str_left_unicode
+
+query
+SELECT s, left(s, 4) FROM test_str_left_unicode
+
+query
+SELECT s, left(s, 0) FROM test_str_left_unicode
diff --git a/spark/src/test/resources/sql-tests/expressions/string/right.sql b/spark/src/test/resources/sql-tests/expressions/string/right.sql
new file mode 100644
index 0000000000..4fb9763bcc
--- /dev/null
+++ b/spark/src/test/resources/sql-tests/expressions/string/right.sql
@@ -0,0 +1,96 @@
+-- Licensed to the Apache Software Foundation (ASF) under one
+-- or more contributor license agreements.  See the NOTICE file
+-- distributed with this work for additional information
+-- regarding copyright ownership.  The ASF licenses this file
+-- to you under the Apache License, Version 2.0 (the
+-- "License"); you may not use this file except in compliance
+-- with the License.  You may obtain a copy of the License at
+--
+--   http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing,
+-- software distributed under the License is distributed on an
+-- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+-- KIND, either express or implied.  See the License for the
+-- specific language governing permissions and limitations
+-- under the License.
+
+-- Note: Right is a RuntimeReplaceable expression. Spark replaces it with
+-- If(IsNull(str), null, If(len <= 0, "", Substring(str, -len, len)))
+-- before Comet sees it. CometRight handles the serde, but the optimizer
+-- may replace it first. We use spark_answer_only to verify correctness.
+
+-- ConfigMatrix: parquet.enable.dictionary=false,true
+
+statement
+CREATE TABLE test_str_right(s string, n int) USING parquet
+
+statement
+INSERT INTO test_str_right VALUES ('hello', 3), ('hello', 0), ('hello', -1), ('hello', 10), ('', 3), (NULL, 3), ('hello', NULL)
+
+-- both columns: len must be literal, falls back
+query spark_answer_only
+SELECT right(s, n) FROM test_str_right
+
+-- column + literal: basic
+query spark_answer_only
+SELECT right(s, 3) FROM test_str_right
+
+-- column + literal: edge cases
+query spark_answer_only
+SELECT right(s, 0) FROM test_str_right
+
+query spark_answer_only
+SELECT right(s, -1) FROM test_str_right
+
+query spark_answer_only
+-- n exceeds length of 'hello' (5 chars)
+SELECT right(s, 10) FROM test_str_right
+
+-- literal + column: falls back
+query spark_answer_only
+SELECT right('hello', n) FROM test_str_right
+
+-- literal + literal
+query spark_answer_only
+SELECT right('hello', 3), right('hello', 0), right('hello', -1), right('', 3), right(NULL, 3)
+
+-- null propagation with len <= 0 (critical: NULL str with non-positive len must return NULL, not empty string)
+query spark_answer_only
+SELECT right(CAST(NULL AS STRING), 0), right(CAST(NULL AS STRING), -1), right(CAST(NULL AS STRING), 2)
+
+-- mixed null and non-null values with len <= 0
+statement
+CREATE TABLE test_str_right_nulls(s string) USING parquet
+
+statement
+INSERT INTO test_str_right_nulls VALUES ('hello'), (NULL), (''), ('world')
+
+query spark_answer_only
+SELECT s, right(s, 0) FROM test_str_right_nulls
+
+query spark_answer_only
+SELECT s, right(s, -1) FROM test_str_right_nulls
+
+query spark_answer_only
+SELECT s, right(s, 2) FROM test_str_right_nulls
+
+-- equivalence with substring
+query spark_answer_only
+SELECT s, right(s, 3), substring(s, -3, 3) FROM test_str_right_nulls
+
+-- unicode
+statement
+CREATE TABLE test_str_right_unicode(s string) USING parquet
+
+statement
+INSERT INTO test_str_right_unicode VALUES ('café'), ('hello世界'), ('😀emoji'), ('తెలుగు'), (NULL)
+
+query spark_answer_only
+SELECT s, right(s, 2) FROM test_str_right_unicode
+
+query spark_answer_only
+SELECT s, right(s, 4) FROM test_str_right_unicode
+
+query spark_answer_only
+SELECT s, right(s, 0) FROM test_str_right_unicode
diff --git a/spark/src/test/scala/org/apache/comet/CometExpressionSuite.scala b/spark/src/test/scala/org/apache/comet/CometExpressionSuite.scala
index 206ac17260..8af177e0bb 100644
--- a/spark/src/test/scala/org/apache/comet/CometExpressionSuite.scala
+++ b/spark/src/test/scala/org/apache/comet/CometExpressionSuite.scala
@@ -523,123 +523,6 @@ class CometExpressionSuite extends CometTestBase with AdaptiveSparkPlanHelper {
     }
   }
 
-  test("LEFT function") {
-    withParquetTable((0 until 10).map(i => (s"test$i", i)), "tbl") {
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, 2) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, 4) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, 0) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, -1) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, 100) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT LEFT(CAST(NULL AS STRING), 2) FROM tbl LIMIT 1")
-    }
-  }
-
-  test("LEFT function with unicode") {
-    val data = Seq("café", "hello世界", "😀emoji", "తెలుగు")
-    withParquetTable(data.zipWithIndex, "unicode_tbl") {
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, 2) FROM unicode_tbl")
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, 3) FROM unicode_tbl")
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, 0) FROM unicode_tbl")
-    }
-  }
-
-  test("LEFT function equivalence with SUBSTRING") {
-    withParquetTable((0 until 20).map(i => Tuple1(s"test$i")), "equiv_tbl") {
-      val df = spark.sql("""
-        SELECT _1,
-          LEFT(_1, 3) as left_result,
-          SUBSTRING(_1, 1, 3) as substring_result
-        FROM equiv_tbl
-      """)
-      checkAnswer(
-        df.filter(
-          "left_result != substring_result OR " +
-            "(left_result IS NULL AND substring_result IS NOT NULL) OR " +
-            "(left_result IS NOT NULL AND substring_result IS NULL)"),
-        Seq.empty)
-    }
-  }
-
-  test("LEFT function with dictionary") {
-    val data = (0 until 1000)
-      .map(_ % 5)
-      .map(i => s"value$i")
-    withParquetTable(data.zipWithIndex, "dict_tbl") {
-      checkSparkAnswerAndOperator("SELECT _1, LEFT(_1, 3) FROM dict_tbl")
-    }
-  }
-
-  test("RIGHT function") {
-    withParquetTable((0 until 10).map(i => (s"test$i", i)), "tbl") {
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 2) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 4) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 0) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, -1) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 100) FROM tbl")
-      checkSparkAnswerAndOperator("SELECT RIGHT(CAST(NULL AS STRING), 2) FROM tbl LIMIT 1")
-    }
-  }
-
-  test("RIGHT function with unicode") {
-    val data = Seq("café", "hello世界", "😀emoji", "తెలుగు")
-    withParquetTable(data.zipWithIndex, "unicode_tbl") {
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 2) FROM unicode_tbl")
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 3) FROM unicode_tbl")
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 0) FROM unicode_tbl")
-    }
-  }
-
-  test("RIGHT function equivalence with SUBSTRING negative pos") {
-    withParquetTable((0 until 20).map(i => Tuple1(s"test$i")), "equiv_tbl") {
-      val df = spark.sql("""
-        SELECT _1,
-          RIGHT(_1, 3) as right_result,
-          SUBSTRING(_1, -3, 3) as substring_result
-        FROM equiv_tbl
-      """)
-      checkAnswer(
-        df.filter(
-          "right_result != substring_result OR " +
-            "(right_result IS NULL AND substring_result IS NOT NULL) OR " +
-            "(right_result IS NOT NULL AND substring_result IS NULL)"),
-        Seq.empty)
-    }
-  }
-
-  test("RIGHT function with dictionary") {
-    val data = (0 until 1000)
-      .map(_ % 5)
-      .map(i => s"value$i")
-    withParquetTable(data.zipWithIndex, "dict_tbl") {
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 3) FROM dict_tbl")
-    }
-  }
-
-  test("RIGHT function NULL handling") {
-    // Test NULL propagation with len = 0 (critical edge case)
-    withParquetTable((0 until 5).map(i => (s"test$i", i)), "null_tbl") {
-      checkSparkAnswerAndOperator("SELECT RIGHT(CAST(NULL AS STRING), 0) FROM null_tbl LIMIT 1")
-      checkSparkAnswerAndOperator("SELECT RIGHT(CAST(NULL AS STRING), -1) FROM null_tbl LIMIT 1")
-      checkSparkAnswerAndOperator("SELECT RIGHT(CAST(NULL AS STRING), -5) FROM null_tbl LIMIT 1")
-    }
-
-    // Test non-NULL strings with len <= 0 (should return empty string)
-    withParquetTable((0 until 5).map(i => (s"test$i", i)), "edge_tbl") {
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, 0) FROM edge_tbl")
-      checkSparkAnswerAndOperator("SELECT _1, RIGHT(_1, -1) FROM edge_tbl")
-    }
-
-    // Test mixed NULL and non-NULL values with a table
-    val table = "right_null_edge"
-    withTable(table) {
-      sql(s"create table $table(str string) using parquet")
-      sql(s"insert into $table values('hello'), (NULL), (''), ('world')")
-      checkSparkAnswerAndOperator(s"SELECT str, RIGHT(str, 0) FROM $table")
-      checkSparkAnswerAndOperator(s"SELECT str, RIGHT(str, -1) FROM $table")
-      checkSparkAnswerAndOperator(s"SELECT str, RIGHT(str, 2) FROM $table")
-    }
-  }
-
   test("hour, minute, second") {
     Seq(true, false).foreach { dictionaryEnabled =>
       withTempDir { dir =>