public void ForbidRange()
        {
            // Arrange
            var filter = new TextEncoderSettings(new OddTextEncoderSettings());

            filter.ForbidRange(UnicodeRanges.Specials);

            // Assert
            for (int i = 0; i <= 0xFFEF; i++)
            {
                Assert.Equal((i % 2) == 1, filter.IsCharacterAllowed((char)i));
            }
            for (int i = 0xFFF0; i <= char.MaxValue; i++)
            {
                Assert.False(filter.IsCharacterAllowed((char)i));
            }
        }
        public void ForbidRange_Null()
        {
            TextEncoderSettings filter = new TextEncoderSettings();

            Assert.Throws <ArgumentNullException>("range", () => filter.ForbidRange(null));
        }