RomanNumerals.RomanNumeralsConverter.NumberToRoman C# (CSharp) Method

        public string NumberToRoman(int number)
        {
            if (number > 3999) throw new ArgumentOutOfRangeException();
            string roman = "";
            int myNumber = number;
            foreach (var item in _lookup)
            {
                while (myNumber >= item.Key)
                {
                    roman += item.Value;
                    myNumber -= item.Key;
                }
            }
            return roman;
        }

        public void Should_Convert_Number_to_Roman(int number, string expected)
        {
            var romNum = new RomanNumeralsConverter();
            var result = romNum.NumberToRoman(number);

            Assert.AreEqual(expected, result);
        }