запишите затмение junit сменный тест

Вот мой уточненный вариант первого ответа. Я надеюсь, что это полезно.

/// <summary>
/// Converts an <see cref="int"/> to its textual representation
/// </summary>
/// <param name="num">
/// The number to convert to text
/// </param>
/// <returns>
/// A textual representation of the given number
/// </returns>
public static string ToText(this int num)
{
    StringBuilder result;

    if (num < 0)
    {
        return string.Format("Minus {0}", ToText(-num));
    }

    if (num == 0)
    {
        return "Zero";
    }

    if (num <= 19)
    {
        var oneToNineteen = new[]
        {
            "One",
            "Two",
            "Three",
            "Four",
            "Five",
            "Six",
            "Seven",
            "Eight",
            "Nine",
            "Ten",
            "Eleven",
            "Twelve",
            "Thirteen",
            "Fourteen",
            "Fifteen",
            "Sixteen",
            "Seventeen",
            "Eighteen",
            "Nineteen"
        };

        return oneToNineteen[num - 1];
    }

    if (num <= 99)
    {
        result = new StringBuilder();

        var multiplesOfTen = new[]
        {
            "Twenty",
            "Thirty",
            "Forty",
            "Fifty",
            "Sixty",
            "Seventy",
            "Eighty",
            "Ninety"
        };

        result.Append(multiplesOfTen[(num / 10) - 2]);

        if (num % 10 != 0)
        {
            result.Append(" ");
            result.Append(ToText(num % 10));
        }

        return result.ToString();
    }

    if (num == 100)
    {
        return "One Hundred";
    }

    if (num <= 199)
    {
        return string.Format("One Hundred and {0}", ToText(num % 100));
    }

    if (num <= 999)
    {
        result = new StringBuilder((num / 100).ToText());
        result.Append(" Hundred");
        if (num % 100 != 0)
        {
            result.Append(" and ");
            result.Append((num % 100).ToText());
        }

        return result.ToString();
    }

    if (num <= 999999)
    {
        result = new StringBuilder((num / 1000).ToText());
        result.Append(" Thousand");
        if (num % 1000 != 0)
        {
            switch ((num % 1000) < 100)
            {
                case true:
                    result.Append(" and ");
                    break;
                case false:
                    result.Append(", ");
                    break;
            }

            result.Append((num % 1000).ToText());
        }

        return result.ToString();
    }

    if (num <= 999999999)
    {
        result = new StringBuilder((num / 1000000).ToText());
        result.Append(" Million");
        if (num % 1000000 != 0)
        {
            switch ((num % 1000000) < 100)
            {
                case true:
                    result.Append(" and ");
                    break;
                case false:
                    result.Append(", ");
                    break;
            }

            result.Append((num % 1000000).ToText());
        }

        return result.ToString();
    }

    result = new StringBuilder((num / 1000000000).ToText());
    result.Append(" Billion");
    if (num % 1000000000 != 0)
    {
        switch ((num % 1000000000) < 100)
        {
            case true:
                result.Append(" and ");
                break;
            case false:
                result.Append(", ");
                break;
        }

        result.Append((num % 1000000000).ToText());
    }

    return result.ToString();
}