public void TestSize()
        {
            var rnd = new System.Random();

            for (var c = 0; c < count; c++)
            {
                var mem   = new byte[sizeof(UInt32) * writeRepeatCount];
                var span1 = new SpanStream(mem);
                var span2 = new SpanStream(mem);
                var a     = new UInt32[writeRepeatCount];

                for (var i = 0; i < writeRepeatCount; i++)
                {
                    var  sr = rnd.Next(0, 4);
                    uint n;
                    switch (sr)
                    {
                    case 0:
                        n = (UInt32)rnd.Next(0, 0b00111111);
                        break;

                    case 1:
                        n = (UInt32)rnd.Next(0b01000000, 0b00111111_11111111);
                        break;

                    case 2:
                        n = (UInt32)rnd.Next(0b01000000_00000000, 0b00111111_11111111_11111111);
                        break;

                    //case 3:
                    default:
                        n = (UInt32)rnd.Next(0b01000000_00000000_00000000, 0b00111111_11111111_11111111_11111111);
                        break;
                    }

                    a[i] = n;
                    span1.WriteSize(n);
                }

                for (var i = 0; i < writeRepeatCount; i++)
                {
                    var r = span2.ReadSize(out var len);
                    Assert.Equal(span2.MeasureWriteSize(a[i]), len);
                    Assert.Equal(a[i], r);
                }
            }
        }