Add test for changing stdout from thread

Author: sergey-miryanov

Lib/test/test_sys_getattr.py

@@ -0,0 +1,47 @@
+import test.support
+from test.support.script_helper import assert_python_failure, assert_python_ok
+import textwrap
+import unittest
+
+
+
+
+@test.support.cpython_only
+class PySysGetAttrTest(unittest.TestCase):
+
+
+    def test_changing_stdout_from_thread(self):
+        # print should use strong reference to the stdout.
+        code = textwrap.dedent('''
+            from contextlib import redirect_stdout
+            from io import StringIO
+            from threading import Thread
+            import time
+
+            class Foo:
+                def __repr__(self):
+                    time.sleep(0.2)
+                    return "Foo"
+
+
+            def thread1():
+                text = StringIO()
+                with redirect_stdout(text):
+                    time.sleep(0.2)
+
+            def main():
+                t1 = Thread(target=thread1, args=())
+                t1.start()
+                time.sleep(0.1)
+                print(Foo())
+
+
+            if __name__ == "__main__":
+                main()
+        ''')
+        rc, out, err = assert_python_ok('-c', code)
+        self.assertEqual(out, b"")
+        self.assertEqual(err, b"")
+
+if __name__ == "__main__":
+    unittest.main()