@Test
public void testSplit_ZeroOne() {

    // split((0, i)) = ((0,i1), (0,i2)), where (i1, i2) = split(i)
    ID[] splitOne = one.split();
    ID[] expected = new ID[] {
        IDs.with(zero, splitOne[0]),
        IDs.with(zero, splitOne[1])
    };
    assertArrayEquals(expected, zeroOne.split());
}