Add test

Author: yuanx749

pandas/tests/extension/test_arrow.py

@@ -2296,6 +2296,16 @@ def test_str_split_pat_none(method):
     tm.assert_series_equal(result, expected)
 
 
+def test_str_split_regex_none():
+    # GH 58321
+    ser = pd.Series(["230/270/270", "240-290-290"], dtype=ArrowDtype(pa.string()))
+    result = ser.str.split(r"/|-", regex=None)
+    expected = pd.Series(
+        ArrowExtensionArray(pa.array([["230", "270", "270"], ["240", "290", "290"]]))
+    )
+    tm.assert_series_equal(result, expected)
+
+
 def test_str_split():
     # GH 52401
     ser = pd.Series(["a1cbcb", "a2cbcb", None], dtype=ArrowDtype(pa.string()))