Add fallback test for lookahead expressions.

Signed-off-by: Igor Peshansky <ipeshansky@nvidia.com>

Author: igorpeshansky

integration_tests/src/main/python/regexp_test.py

@@ -1040,6 +1040,16 @@ def test_rlike_fallback_possessive_quantifier():
             'RLike',
             conf=_regexp_conf)
 
+@allow_non_gpu('ProjectExec', 'RLike')
+def test_rlike_fallback_lookaheads():
+    gen = mk_str_gen('(\u20ac|\\w){0,3}a[|b*.$\r\n]{0,2}c\\w{0,3}')
+    for pattern in ['a(?=a*)', 'a(?!a*)']:
+        assert_gpu_fallback_collect(
+            lambda spark, pattern=pattern: unary_op_df(spark, gen).selectExpr(
+                f'a rlike "{pattern}"'),
+            'RLike',
+            conf=_regexp_conf)
+
 def test_regexp_extract_all_idx_zero():
     gen = mk_str_gen('[abcd]{0,3}[0-9]{0,3}-[0-9]{0,3}[abcd]{1,3}')
     assert_gpu_and_cpu_are_equal_collect(

tests/src/test/scala/com/nvidia/spark/rapids/RegularExpressionParserSuite.scala

@@ -248,6 +248,18 @@ class RegularExpressionParserSuite extends AnyFunSuite {
         RegexRepetition(RegexChar('a'), SimpleQuantifier('?')))), None))))
   }
 
+  test("lookahead group expressions") {
+    val e = intercept[RegexUnsupportedException] {
+      parse("a(?=abc)b")
+    }
+    assert(e.getMessage.startsWith("Lookahead group expressions are not supported"))
+
+    val e = intercept[RegexUnsupportedException] {
+      parse("a(?!abc)b")
+    }
+    assert(e.getMessage.startsWith("Lookahead group expressions are not supported"))
+  }
+
   test("complex expression") {
     val ast = parse(
       "^" +            // start of line