public void Test_roundtrip(NumberConversion numberConversion)
        {
            NullableBigIntegerConverter converter = new NullableBigIntegerConverter(numberConversion);

            TestConverter(null, (integer, bigInteger) => integer.Equals(bigInteger), converter);
            TestConverter(int.MaxValue, (integer, bigInteger) => integer.Equals(bigInteger), converter);
            TestConverter(BigInteger.One, (integer, bigInteger) => integer.Equals(bigInteger), converter);
            TestConverter(BigInteger.Zero, (integer, bigInteger) => integer.Equals(bigInteger), converter);
        }
        public void Can_read_null()
        {
            NullableBigIntegerConverter converter = new NullableBigIntegerConverter();
            JsonReader reader = new JsonTextReader(new StringReader("null"));

            reader.ReadAsString();
            BigInteger?result = converter.ReadJson(reader, typeof(BigInteger?), BigInteger.Zero, false, JsonSerializer.CreateDefault());

            Assert.AreEqual(null, result);
        }