public void ForbidChars_String() { // Arrange var filter = new CodePointFilter(UnicodeRanges.BasicLatin); // Act var retVal = filter.ForbidChars("xz"); // Assert Assert.Same(filter, retVal); // returns 'this' instance Assert.True(filter.IsCharacterAllowed('w')); Assert.False(filter.IsCharacterAllowed('x')); Assert.True(filter.IsCharacterAllowed('y')); Assert.False(filter.IsCharacterAllowed('z')); }