======================================================================
FAIL: test_resolve_common (test.test_pathlib.PathTest)
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Traceback (most recent call last):
  File "C:\workspace\cpython-3.8a\lib\test\test_pathlib.py", line 1538, in test_resolve_common
    self._check_resolve_relative(p, P(d, 'foo', 'in', 'spam'), False)
  File "C:\workspace\cpython-3.8a\lib\test\test_pathlib.py", line 1477, in _check_resolve
    self.assertEqual(q, expected)
AssertionError: WindowsPath('C:/Users/longusername/AppData/Local/Temp/tmpbenaiqaa-[
13 chars]pam') != WindowsPath('C:/Users/LONGUS~1/AppData/Local/Temp/tmpbenaiqaa-
dirD/foo/in/spam')

======================================================================

The problem is that the temporary directory path returned by tempfile.mkdtemp() contains the username in "short" (8.3) format, but Path.resolve() converts short names to long ones (thanks to ntpath._getfinalpathname()).

Since os.path.realpath() still doesn't resolve symlinks on Windows (#9949, #14094), and users of ntpath._getfinalpathname() have to deal with '\\?\' prefix, I think I'll just use Path.resolve() for the tmp dir path as a workaround.