Add tests for regexp() and regexp_like() [databricks] (NVIDIA#4093)

* Add tests for regexp and regexplike (synonyms for RLike)

Signed-off-by: Andy Grove <andygrove@nvidia.com>

* add import

integration_tests/src/main/python/string_test.py

@@ -20,6 +20,7 @@
 from marks import *
 from pyspark.sql.types import *
 import pyspark.sql.functions as f
+from spark_session import is_before_spark_320
 
 def mk_str_gen(pattern):
     return StringGen(pattern).with_special_case('').with_special_pattern('.{0,10}')
@@ -483,6 +484,28 @@ def test_regexp_replace():
                 'regexp_replace(a, "a|b|c", "A")'),
             conf={'spark.rapids.sql.expression.RegExpReplace': 'true'})
 
+@pytest.mark.skipif(is_before_spark_320(), reason='regexp is synonym for RLike starting in Spark 3.2.0')
+def test_regexp():
+    gen = mk_str_gen('[abcd]{1,3}')
+    assert_gpu_and_cpu_are_equal_collect(
+            lambda spark: unary_op_df(spark, gen).selectExpr(
+                'regexp(a, "a{2}")',
+                'regexp(a, "a{1,3}")',
+                'regexp(a, "a{1,}")',
+                'regexp(a, "a[bc]d")'),
+            conf={'spark.rapids.sql.expression.RLike': 'true'})
+
+@pytest.mark.skipif(is_before_spark_320(), reason='regexp_like is synonym for RLike starting in Spark 3.2.0')
+def test_regexp_like():
+    gen = mk_str_gen('[abcd]{1,3}')
+    assert_gpu_and_cpu_are_equal_collect(
+            lambda spark: unary_op_df(spark, gen).selectExpr(
+                'regexp_like(a, "a{2}")',
+                'regexp_like(a, "a{1,3}")',
+                'regexp_like(a, "a{1,}")',
+                'regexp_like(a, "a[bc]d")'),
+            conf={'spark.rapids.sql.expression.RLike': 'true'})
+
 @pytest.mark.skipif(is_databricks_runtime(),
     reason='Databricks optimizes out regexp_replace call in this case')
 @allow_non_gpu('ProjectExec', 'RegExpReplace')