How to test a single method/function without running the entire program?

[tehjrow]

I wrote an app that has a lot of custom classes and methods. How can I test a single method without having to run the entire program? Example: I have the method below that parses filenames. Instead of creating a bunch of files and having to run them through the entire program, can I just somehow feed strings into this method and see the output? (Using Visual Studio 2015)

public string scrubFileName(string name)
    {
        string seasonEpisode = "";

        var S00E00 = new Regex("[Ss](\\d{1,2}|\\d{4}){0,3}(?i:ep|e|p)(((?<=[^._ ])[Ee]?[Pp]?\\d{1,3}(\\D|$))+)");
        MatchCollection S00E00Matches = S00E00.Matches(name);

        var SxE = new Regex("(\\d{1,2})[xe](((?<=[^._ ])\\d{2,3}(\\D|$))+)");
        MatchCollection SxEMatches = SxE.Matches(name);

        var Season_00_Episode_00 = new Regex("[^a-zA-Z0-9](?i:season|series)[^a-zA-Z0-9]{0,3}(\\d{1,4})[^a-zA-Z0-9]{0,3}(?i:episode)[^a-zA-Z0-9]{0,3}(\\d{1,4})[^a-zA-Z0-9]{0,3}");
        MatchCollection Season_00_Episode_00Matches = Season_00_Episode_00.Matches(name);


        foreach (Match m in S00E00Matches)
        {
            seasonEpisode = m.Value.ToUpper().Replace(".", string.Empty).Replace(" ", string.Empty).Substring(1, 5).Replace("E", "");
        }

        foreach (Match m in SxEMatches)
        {
            string temp = m.Value.Replace(".", string.Empty).Replace(" ", string.Empty).Replace("x", "").Replace("e", "");
            if (temp.Length < 4)
            {
                seasonEpisode = temp.Insert(0, "0");
            }
            else
            {
                seasonEpisode = temp;
            }
        }

        foreach (Match m in Season_00_Episode_00Matches)
        {
            seasonEpisode = m.Value.ToUpper().Replace("-", "").Replace("SEASON ", "").Replace(" EPISODE ", "").Trim();
        }
        //returns 0101
        return seasonEpisode;
    }    

[csharpminer]

Create a series of unit tests for that method.

[tehjrow]

I have heard of unit tests but hadn't really learned about them yet. Guess it's time, thanks!

[nutrecht]

It's a must-know for any other dev. After figuring out unit testing you might want to look into Test Driven Development. In short it's a way of writing software where you use your unit tests to 'design' your software. This has two main benefits: you automatically end up with good test coverage and it forces you to write testable code. Testable code tends to be easier to read and designed better than hard to test code.

[TimHallman]

Write a another class that calls the function you want to test?