public void Test_roundtrip(NumberConversion numberConversion)
        {
            NullableUInt256Converter converter = new NullableUInt256Converter(numberConversion);

            TestConverter(null, (integer, bigInteger) => integer.Equals(bigInteger), converter);
            TestConverter(int.MaxValue, (integer, bigInteger) => integer.Equals(bigInteger), converter);
            TestConverter(UInt256.One, (integer, bigInteger) => integer.Equals(bigInteger), converter);
            TestConverter(UInt256.Zero, (integer, bigInteger) => integer.Equals(bigInteger), converter);
        }
        public void Can_read_1()
        {
            NullableUInt256Converter converter = new NullableUInt256Converter();
            JsonReader reader = new JsonTextReader(new StringReader("1"));

            reader.ReadAsString();
            UInt256?result = converter.ReadJson(reader, typeof(UInt256?), UInt256.Zero, false, JsonSerializer.CreateDefault());

            Assert.AreEqual(UInt256.Parse("1"), result);
        }