gh-110147: test_msvcrt: run console I/O tests in new processes (#110268)

Lib/test/test_msvcrt.py

@@ -1,17 +1,17 @@
 import os
+import subprocess
 import sys
 import unittest
+from textwrap import dedent
 
-from test.support import os_helper
+from test.support import os_helper, requires_resource
 from test.support.os_helper import TESTFN, TESTFN_ASCII
 
 if sys.platform != "win32":
     raise unittest.SkipTest("windows related tests")
 
 import _winapi
-import msvcrt;
-
-from _testconsole import write_input, flush_console_input_buffer
+import msvcrt
 
 
 class TestFileOperations(unittest.TestCase):
@@ -61,34 +61,45 @@ c_encoded = b'\x57\x5b' # utf-16-le (which windows internally used) encoded char
 
 
 class TestConsoleIO(unittest.TestCase):
+    # CREATE_NEW_CONSOLE creates a "popup" window.
+    @requires_resource('gui')
+    def run_in_separated_process(self, code):
+        # Run test in a seprated process to avoid stdin conflicts.
+        # See: gh-110147
+        cmd = [sys.executable, '-c', code]
+        subprocess.run(cmd, check=True, capture_output=True,
+                       creationflags=subprocess.CREATE_NEW_CONSOLE)
+
     def test_kbhit(self):
-        h = msvcrt.get_osfhandle(sys.stdin.fileno())
-        flush_console_input_buffer(h)
-        self.assertEqual(msvcrt.kbhit(), 0)
+        code = dedent('''
+            import msvcrt
+            assert msvcrt.kbhit() == 0
+        ''')
+        self.run_in_separated_process(code)
 
     def test_getch(self):
         msvcrt.ungetch(b'c')
         self.assertEqual(msvcrt.getch(), b'c')
 
-    def test_getwch(self):
-        with open('CONIN$', 'rb', buffering=0) as stdin:
-            h = msvcrt.get_osfhandle(stdin.fileno())
-            flush_console_input_buffer(h)
+    def check_getwch(self, funcname):
+        code = dedent(f'''
+            import msvcrt
+            from _testconsole import write_input
+            with open("CONIN$", "rb", buffering=0) as stdin:
+                write_input(stdin, {ascii(c_encoded)})
+                assert msvcrt.{funcname}() == "{c}"
+        ''')
+        self.run_in_separated_process(code)
 
-            write_input(stdin, c_encoded)
-            self.assertEqual(msvcrt.getwch(), c)
+    def test_getwch(self):
+        self.check_getwch('getwch')
 
     def test_getche(self):
         msvcrt.ungetch(b'c')
         self.assertEqual(msvcrt.getche(), b'c')
 
     def test_getwche(self):
-        with open('CONIN$', 'rb', buffering=0) as stdin:
-            h = msvcrt.get_osfhandle(stdin.fileno())
-            flush_console_input_buffer(h)
-
-            write_input(stdin, c_encoded)
-            self.assertEqual(msvcrt.getwche(), c)
+        self.check_getwch('getwche')
 
     def test_putch(self):
         msvcrt.putch(b'c')