public void AndNotBigInteger()
        {
            foreach (BigInteger[] element in booleanPairs)
            {
                BigInteger i1 = element[0], i2 = element[1];
                BigInteger res = BigMath.AndNot(i1, i2);
                int        len = System.Math.Max(i1.BitLength, i2.BitLength) + 66;
                for (int i = 0; i < len; i++)
                {
                    Assert.True((BigInteger.TestBit(i1, i) && !BigInteger.TestBit(i2, i)) == BigInteger.TestBit(res, i), "andNot");
                }

                // asymmetrical
                i1  = element[1];
                i2  = element[0];
                res = BigMath.AndNot(i1, i2);
                for (int i = 0; i < len; i++)
                {
                    Assert.True((BigInteger.TestBit(i1, i) && !BigInteger.TestBit(i2, i)) == BigInteger.TestBit(res, i), "andNot reversed");
                }
            }

            Assert.Throws <NullReferenceException>(() => BigMath.AndNot(BigInteger.Zero, null));

            BigInteger bi = new BigInteger(0, new byte[] { });

            Assert.Equal(BigInteger.Zero, BigMath.AndNot(bi, BigInteger.Zero));
        }