public void XorTest()
{
NodeId zero = new NodeId(new byte[20]);
byte[] b = new byte[20]; b[0] = 1;
NodeId one = new NodeId(b);
NodeId r = one.Xor(zero);
Assert.AreEqual(one, r, "#1");
Assert.IsTrue(one > zero, "#2");
Assert.IsTrue(one.CompareTo(zero) > 0, "#3");
NodeId z = one.Xor(r);
Assert.AreEqual(zero, z, "#4");
}