def METHOD_NAME(self):
    for aa in self.randombitarrays():
        for b in self.randombitarrays():
            a = aa.copy()
            s = BitArray(a)
            t = BitArray(b)
            s.extend(t)
            a.extend(b)
            self.check(s, a)
        s = BitArray(aa)
        s.extend(s)
        self.check(s, 2 * aa)