A small helper program that does the equavalent of this should also work:

import Cocoa
Cocoa.NSWindow.alloc().initWithContentRect_styleMask_backing_defer_(((10, 10), (100, 100)), 0, 0, 0)

If this code raises an exception you cannot create windows, if it doesn't you can. This doesn't actually show the window and shouldn't mess up the users desktop when running the testsuite interactively.