add tests for str and pyarrow strings

Author: aaronchucarroll

pandas/tests/strings/test_get_dummies.py

@@ -40,6 +40,7 @@ def test_get_dummies_index():
     tm.assert_index_equal(result, expected)
 
 
+# GH#47872
 @pytest.mark.parametrize(
     "dtype",
     [
@@ -67,6 +68,7 @@ def test_get_dummies_with_dtype(any_string_dtype, dtype):
     tm.assert_frame_equal(result, expected)
 
 
+# GH#47872
 @td.skip_if_no("pyarrow")
 @pytest.mark.parametrize(
     "dtype",
@@ -91,3 +93,31 @@ def test_get_dummies_with_pyarrow_dtype(any_string_dtype, dtype):
         dtype=dtype,
     )
     tm.assert_frame_equal(result, expected)
+
+
+# GH#47872
+def test_get_dummies_with_str_dtype(any_string_dtype):
+    s = Series(["a|b", "a|c", np.nan], dtype=any_string_dtype)
+    result = s.str.get_dummies("|", dtype=str)
+    expected = DataFrame(
+        [["T", "T", "F"], ["T", "F", "T"], ["F", "F", "F"]],
+        columns=list("abc"),
+        dtype=str,
+    )
+    tm.assert_frame_equal(result, expected)
+
+
+# GH#47872
+def test_get_dummies_with_pa_str_dtype(any_string_dtype):
+    s = Series(["a|b", "a|c", np.nan], dtype=any_string_dtype)
+    result = s.str.get_dummies("|", dtype="str[pyarrow]")
+    expected = DataFrame(
+        [
+            ["true", "true", "false"],
+            ["true", "false", "true"],
+            ["false", "false", "false"],
+        ],
+        columns=list("abc"),
+        dtype="str[pyarrow]",
+    )
+    tm.assert_frame_equal(result, expected)