Replace custom class with TextIOWrapper

Tests/test_file_png.py

@@ -4,7 +4,7 @@ import re
 import sys
 import warnings
 import zlib
-from io import BytesIO
+from io import BytesIO, TextIOWrapper
 from pathlib import Path
 from types import ModuleType
 from typing import Any, cast
@@ -821,19 +821,15 @@ class TestFilePng:
     @pytest.mark.parametrize("buffer", (True, False))
     def test_save_stdout(self, buffer: bool, monkeypatch: pytest.MonkeyPatch) -> None:
 
-        class MyStdOut:
-            buffer = BytesIO()
-
-        mystdout: MyStdOut | BytesIO = MyStdOut() if buffer else BytesIO()
+        fp = BytesIO()
+        mystdout = TextIOWrapper(fp) if buffer else fp
 
         monkeypatch.setattr(sys, "stdout", mystdout)
 
         with Image.open(TEST_PNG_FILE) as im:
             im.save(sys.stdout, "PNG")  # type: ignore[arg-type]
 
-        if isinstance(mystdout, MyStdOut):
-            mystdout = mystdout.buffer
-        with Image.open(mystdout) as reloaded:
+        with Image.open(fp) as reloaded:
             assert_image_equal_tofile(reloaded, TEST_PNG_FILE)
 
     def test_truncated_end_chunk(self, monkeypatch: pytest.MonkeyPatch) -> None:

Tests/test_file_ppm.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import sys
-from io import BytesIO
+from io import BytesIO, TextIOWrapper
 from pathlib import Path
 
 import pytest
@@ -381,17 +381,13 @@ def test_mimetypes(tmp_path: Path) -> None:
 @pytest.mark.parametrize("buffer", (True, False))
 def test_save_stdout(buffer: bool, monkeypatch: pytest.MonkeyPatch) -> None:
 
-    class MyStdOut:
-        buffer = BytesIO()
-
-    mystdout: MyStdOut | BytesIO = MyStdOut() if buffer else BytesIO()
+    fp = BytesIO()
+    mystdout = TextIOWrapper(fp) if buffer else fp
 
     monkeypatch.setattr(sys, "stdout", mystdout)
 
     with Image.open(TEST_FILE) as im:
         im.save(sys.stdout, "PPM")  # type: ignore[arg-type]
 
-    if isinstance(mystdout, MyStdOut):
-        mystdout = mystdout.buffer
-    with Image.open(mystdout) as reloaded:
+    with Image.open(fp) as reloaded:
         assert_image_equal_tofile(reloaded, TEST_FILE)