chore: add test for all optional arguments

Author: mesejo

python/tests/test_functions.py

@@ -780,6 +780,25 @@ def test_array_function_obj_tests(stmt, py_expr):
             f.regexp_instr(column("a"), literal("([lr])"), n=literal(2)),
             pa.array([4, 4, 0], type=pa.int64()),
         ),
+        (
+            f.regexp_instr(
+                column("a"),
+                literal("(x)?([hw])"),
+                start=literal(1),
+                n=literal(1),
+                flags=literal("i"),
+                sub_expr=literal(2),
+            ),
+            pa.array([1, 1, 0], type=pa.int64()),
+        ),
+        (
+            f.regexp_instr(column("a"), literal("([hw])"), flags=literal("i")),
+            pa.array([1, 1, 0], type=pa.int64()),
+        ),
+        (
+            f.regexp_instr(column("a"), literal("(x)?([HW])"), sub_expr=literal(2)),
+            pa.array([1, 1, 0], type=pa.int64()),
+        ),
     ],
 )
 def test_string_functions(df, function, expected_result):