diff --git a/datafusion/core/tests/sql/mod.rs b/datafusion/core/tests/sql/mod.rs
index cbccf333b304..529d0313cac2 100644
--- a/datafusion/core/tests/sql/mod.rs
+++ b/datafusion/core/tests/sql/mod.rs
@@ -106,8 +106,6 @@ pub mod parquet_schema;
 pub mod partitioned_csv;
 pub mod set_variable;
 pub mod subqueries;
-#[cfg(feature = "unicode_expressions")]
-pub mod unicode;
 
 fn assert_float_eq<T>(expected: &[Vec<T>], received: &[Vec<String>])
 where
diff --git a/datafusion/core/tests/sql/unicode.rs b/datafusion/core/tests/sql/unicode.rs
deleted file mode 100644
index b787b5a328cb..000000000000
--- a/datafusion/core/tests/sql/unicode.rs
+++ /dev/null
@@ -1,128 +0,0 @@
-// 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.
-
-use super::*;
-
-#[tokio::test]
-async fn query_length() -> Result<()> {
-    generic_query_length::<StringArray>(DataType::Utf8).await
-}
-
-#[tokio::test]
-async fn query_large_length() -> Result<()> {
-    generic_query_length::<LargeStringArray>(DataType::LargeUtf8).await
-}
-
-#[tokio::test]
-async fn test_unicode_expressions() -> Result<()> {
-    test_expression!("char_length('')", "0");
-    test_expression!("char_length('chars')", "5");
-    test_expression!("char_length('josé')", "4");
-    test_expression!("char_length(NULL)", "NULL");
-    test_expression!("character_length('')", "0");
-    test_expression!("character_length('chars')", "5");
-    test_expression!("character_length('josé')", "4");
-    test_expression!("character_length(NULL)", "NULL");
-    test_expression!("left('abcde', -2)", "abc");
-    test_expression!("left('abcde', -200)", "");
-    test_expression!("left('abcde', 0)", "");
-    test_expression!("left('abcde', 2)", "ab");
-    test_expression!("left('abcde', 200)", "abcde");
-    test_expression!("left('abcde', CAST(NULL AS INT))", "NULL");
-    test_expression!("left(NULL, 2)", "NULL");
-    test_expression!("left(NULL, CAST(NULL AS INT))", "NULL");
-    test_expression!("length('')", "0");
-    test_expression!("length('chars')", "5");
-    test_expression!("length('josé')", "4");
-    test_expression!("length(NULL)", "NULL");
-    test_expression!("lpad('hi', -1, 'xy')", "");
-    test_expression!("lpad('hi', 5, 'xy')", "xyxhi");
-    test_expression!("lpad('hi', -1)", "");
-    test_expression!("lpad('hi', 0)", "");
-    test_expression!("lpad('hi', 21, 'abcdef')", "abcdefabcdefabcdefahi");
-    test_expression!("lpad('hi', 5, 'xy')", "xyxhi");
-    test_expression!("lpad('hi', 5, NULL)", "NULL");
-    test_expression!("lpad('hi', 5)", "   hi");
-    test_expression!("lpad('hi', CAST(NULL AS INT), 'xy')", "NULL");
-    test_expression!("lpad('hi', CAST(NULL AS INT))", "NULL");
-    test_expression!("lpad('xyxhi', 3)", "xyx");
-    test_expression!("lpad(NULL, 0)", "NULL");
-    test_expression!("lpad(NULL, 5, 'xy')", "NULL");
-    test_expression!("reverse('abcde')", "edcba");
-    test_expression!("reverse('loẅks')", "sk̈wol"); // Compatible with PostgreSQL
-    test_expression!("reverse(NULL)", "NULL");
-    test_expression!("right('abcde', -2)", "cde");
-    test_expression!("right('abcde', -200)", "");
-    test_expression!("right('abcde', 0)", "");
-    test_expression!("right('abcde', 2)", "de");
-    test_expression!("right('abcde', 200)", "abcde");
-    test_expression!("right('abcde', CAST(NULL AS INT))", "NULL");
-    test_expression!("right(NULL, 2)", "NULL");
-    test_expression!("right(NULL, CAST(NULL AS INT))", "NULL");
-    test_expression!("rpad('hi', -1, 'xy')", "");
-    test_expression!("rpad('hi', 5, 'xy')", "hixyx");
-    test_expression!("rpad('hi', -1)", "");
-    test_expression!("rpad('hi', 0)", "");
-    test_expression!("rpad('hi', 21, 'abcdef')", "hiabcdefabcdefabcdefa");
-    test_expression!("rpad('hi', 5, 'xy')", "hixyx");
-    test_expression!("rpad('hi', 5, NULL)", "NULL");
-    test_expression!("rpad('hi', 5)", "hi   ");
-    test_expression!("rpad('hi', CAST(NULL AS INT), 'xy')", "NULL");
-    test_expression!("rpad('hi', CAST(NULL AS INT))", "NULL");
-    test_expression!("rpad('xyxhi', 3)", "xyx");
-    test_expression!("strpos('abc', 'c')", "3");
-    test_expression!("strpos('josé', 'é')", "4");
-    test_expression!("strpos('joséésoj', 'so')", "6");
-    test_expression!("strpos('joséésoj', 'abc')", "0");
-    test_expression!("strpos(NULL, 'abc')", "NULL");
-    test_expression!("strpos('joséésoj', NULL)", "NULL");
-    test_expression!("substr('alphabet', -3)", "alphabet");
-    test_expression!("substr('alphabet', 0)", "alphabet");
-    test_expression!("substr('alphabet', 1)", "alphabet");
-    test_expression!("substr('alphabet', 2)", "lphabet");
-    test_expression!("substr('alphabet', 3)", "phabet");
-    test_expression!("substr('alphabet', 30)", "");
-    test_expression!("substr('alphabet', CAST(NULL AS int))", "NULL");
-    test_expression!("substr('alphabet', 3, 2)", "ph");
-    test_expression!("substr('alphabet', 3, 20)", "phabet");
-    test_expression!("substr('alphabet', CAST(NULL AS int), 20)", "NULL");
-    test_expression!("substr('alphabet', 3, CAST(NULL AS int))", "NULL");
-    test_expression!("translate('12345', '143', 'ax')", "a2x5");
-    test_expression!("translate(NULL, '143', 'ax')", "NULL");
-    test_expression!("translate('12345', NULL, 'ax')", "NULL");
-    test_expression!("translate('12345', '143', NULL)", "NULL");
-    Ok(())
-}
-
-async fn generic_query_length<T: 'static + Array + From<Vec<&'static str>>>(
-    datatype: DataType,
-) -> Result<()> {
-    let schema = Arc::new(Schema::new(vec![Field::new("c1", datatype, false)]));
-
-    let data = RecordBatch::try_new(
-        schema.clone(),
-        vec![Arc::new(T::from(vec!["", "a", "aa", "aaa"]))],
-    )?;
-
-    let ctx = SessionContext::new();
-    ctx.register_batch("test", data)?;
-    let sql = "SELECT length(c1) FROM test";
-    let actual = execute(&ctx, sql).await;
-    let expected = vec![vec!["0"], vec!["1"], vec!["2"], vec!["3"]];
-    assert_eq!(expected, actual);
-    Ok(())
-}
diff --git a/datafusion/core/tests/sqllogictests/test_files/functions.slt b/datafusion/core/tests/sqllogictests/test_files/functions.slt
new file mode 100644
index 000000000000..c6f2db8eb233
--- /dev/null
+++ b/datafusion/core/tests/sqllogictests/test_files/functions.slt
@@ -0,0 +1,420 @@
+# 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.
+
+
+# unicode expressions
+
+query I
+SELECT char_length('')
+----
+0
+
+query I
+SELECT char_length('chars')
+----
+5
+
+query I
+SELECT char_length('josé')
+----
+4
+
+query ?
+SELECT char_length(NULL)
+----
+NULL
+
+query I
+SELECT character_length('')
+----
+0
+
+query I
+SELECT character_length('chars')
+----
+5
+
+query I
+SELECT character_length('josé')
+----
+4
+
+query ?
+SELECT character_length(NULL)
+----
+NULL
+
+query T
+SELECT left('abcde', -2)
+----
+abc
+
+query T
+SELECT left('abcde', -200)
+----
+(empty)
+
+query T
+SELECT left('abcde', 0)
+----
+(empty)
+
+query T
+SELECT left('abcde', 2)
+----
+ab
+
+query T
+SELECT left('abcde', 200)
+----
+abcde
+
+query T
+SELECT left('abcde', CAST(NULL AS INT))
+----
+NULL
+
+query ?
+SELECT left(NULL, 2)
+----
+NULL
+
+query ?
+SELECT left(NULL, CAST(NULL AS INT))
+----
+NULL
+
+query I
+SELECT length('')
+----
+0
+
+query I
+SELECT length('chars')
+----
+5
+
+query I
+SELECT length('josé')
+----
+4
+
+query ?
+SELECT length(NULL)
+----
+NULL
+
+query T
+SELECT lpad('hi', -1, 'xy')
+----
+(empty)
+
+query T
+SELECT lpad('hi', 5, 'xy')
+----
+xyxhi
+
+query T
+SELECT lpad('hi', -1)
+----
+(empty)
+
+query T
+SELECT lpad('hi', 0)
+----
+(empty)
+
+query T
+SELECT lpad('hi', 21, 'abcdef')
+----
+abcdefabcdefabcdefahi
+
+query T
+SELECT lpad('hi', 5, 'xy')
+----
+xyxhi
+
+query T
+SELECT lpad('hi', 5, NULL)
+----
+NULL
+
+query T
+SELECT lpad('hi', 5)
+----
+   hi
+
+query T
+SELECT lpad('hi', CAST(NULL AS INT), 'xy')
+----
+NULL
+
+query T
+SELECT lpad('hi', CAST(NULL AS INT))
+----
+NULL
+
+query T
+SELECT lpad('xyxhi', 3)
+----
+xyx
+
+query ?
+SELECT lpad(NULL, 0)
+----
+NULL
+
+query ?
+SELECT lpad(NULL, 5, 'xy')
+----
+NULL
+
+query T
+SELECT reverse('abcde')
+----
+edcba
+
+query T
+SELECT reverse('loẅks')
+----
+sk̈wol
+
+query ?
+SELECT reverse(NULL)
+----
+NULL
+
+query T
+SELECT right('abcde', -2)
+----
+cde
+
+query T
+SELECT right('abcde', -200)
+----
+(empty)
+
+query T
+SELECT right('abcde', 0)
+----
+(empty)
+
+query T
+SELECT right('abcde', 2)
+----
+de
+
+query T
+SELECT right('abcde', 200)
+----
+abcde
+
+query T
+SELECT right('abcde', CAST(NULL AS INT))
+----
+NULL
+
+query ?
+SELECT right(NULL, 2)
+----
+NULL
+
+query ?
+SELECT right(NULL, CAST(NULL AS INT))
+----
+NULL
+
+query T
+SELECT rpad('hi', -1, 'xy')
+----
+(empty)
+
+query T
+SELECT rpad('hi', 5, 'xy')
+----
+hixyx
+
+query T
+SELECT rpad('hi', -1)
+----
+(empty)
+
+query T
+SELECT rpad('hi', 0)
+----
+(empty)
+
+query T
+SELECT rpad('hi', 21, 'abcdef')
+----
+hiabcdefabcdefabcdefa
+
+query T
+SELECT rpad('hi', 5, 'xy')
+----
+hixyx
+
+query T
+SELECT rpad('hi', 5, NULL)
+----
+NULL
+
+query T
+SELECT rpad('hi', 5)
+----
+hi   
+
+query T
+SELECT rpad('hi', CAST(NULL AS INT), 'xy')
+----
+NULL
+
+query T
+SELECT rpad('hi', CAST(NULL AS INT))
+----
+NULL
+
+query T
+SELECT rpad('xyxhi', 3)
+----
+xyx
+
+query I
+SELECT strpos('abc', 'c')
+----
+3
+
+query I
+SELECT strpos('josé', 'é')
+----
+4
+
+query I
+SELECT strpos('joséésoj', 'so')
+----
+6
+
+query I
+SELECT strpos('joséésoj', 'abc')
+----
+0
+
+query ?
+SELECT strpos(NULL, 'abc')
+----
+NULL
+
+query I
+SELECT strpos('joséésoj', NULL)
+----
+NULL
+
+query T
+SELECT substr('alphabet', -3)
+----
+alphabet
+
+query T
+SELECT substr('alphabet', 0)
+----
+alphabet
+
+query T
+SELECT substr('alphabet', 1)
+----
+alphabet
+
+query T
+SELECT substr('alphabet', 2)
+----
+lphabet
+
+query T
+SELECT substr('alphabet', 3)
+----
+phabet
+
+query T
+SELECT substr('alphabet', 30)
+----
+(empty)
+
+query T
+SELECT substr('alphabet', CAST(NULL AS int))
+----
+NULL
+
+query T
+SELECT substr('alphabet', 3, 2)
+----
+ph
+
+query T
+SELECT substr('alphabet', 3, 20)
+----
+phabet
+
+query T
+SELECT substr('alphabet', CAST(NULL AS int), 20)
+----
+NULL
+
+query T
+SELECT substr('alphabet', 3, CAST(NULL AS int))
+----
+NULL
+
+query T
+SELECT translate('12345', '143', 'ax')
+----
+a2x5
+
+query ?
+SELECT translate(NULL, '143', 'ax')
+----
+NULL
+
+query T
+SELECT translate('12345', NULL, 'ax')
+----
+NULL
+
+query T
+SELECT translate('12345', '143', NULL)
+----
+NULL
+
+statement ok
+CREATE TABLE test(
+  c1 VARCHAR
+) as VALUES
+(''),
+('a'),
+('aa'),
+('aaa');
+
+# generic query length
+query I rowsort
+SELECT length(c1) FROM test
+----
+0
+1
+2
+3
+
+statement ok
+drop table test