public void TryConvertToTokenStream_ReturnsFailureResult_WhenInputStreamContainsInvalidCharacter()
{
_parserFactory.TryGetTokenParser(Arg.Any <string>(), out _).Returns(false);
_input.IsEmpty().Returns(false);
var lexer = new Lexer(_parserFactory);
var result = lexer.TryConvertToTokenStream(_input, out _);
Assert.IsFalse(result.IsSuccess);
_input.Received(1).IsEmpty();
_parserFactory.Received(1).TryGetTokenParser(Arg.Any <string>(), out _);
}