test_support.test_change_cwd is failing on macOS

The test exercises support.change_cwd which basically does:

def change_cwd(path):
    saved_dir = os.getcwd()
    os.chdir(path)
    try:
        yield os.getcwd()
    finally:
        os.chdir(saved_dir)

and then checks that the directory is what's expected. However this is failing with an assertion error:

AssertionError: '/private/var/folders/some_folder' != '/var/folders/some_folder'

Start with the test_support.test_change_cwd test and the support.change_cwd implementation shown in the issue, then reproduce the assertion on macOS. Compare the expected and returned paths after changing directories; done means the test correctly handles the observed macOS path while still verifying the changed working directory.