'Check that %run doesn\'t damage __builtins__'

def test_builtins_id(self):

    _ip = get_ipython()
    bid1 = id(_ip.user_ns['__builtins__'])
    self.run_tmpfile()
    bid2 = id(_ip.user_ns['__builtins__'])
    nt.assert_equal(bid1, bid2)
