def test_cross(self):
        for w in 1, 2, 3, 4:
            self.assertEqual(audioop.cross(b'', w), -1)
            self.assertEqual(audioop.cross(bytearray(), w), -1)
            self.assertEqual(audioop.cross(memoryview(b''), w), -1)
            p = packs[w]
            self.assertEqual(audioop.cross(p(0, 1, 2), w), 0)
            self.assertEqual(audioop.cross(p(1, 2, -3, -4), w), 1)
            self.assertEqual(audioop.cross(p(-1, -2, 3, 4), w), 1)
            self.assertEqual(audioop.cross(p(0, minvalues[w]), w), 1)
            self.assertEqual(audioop.cross(p(minvalues[w], maxvalues[w]), w), 1)