So what is a Unit Test

public class StringSplitter
{
    public  ArrayList<String> splitString( String tags )
    {
        String regex = ",\\ *";
        
        return splitStringUsingRegex(regex, tags);
        
    }
    
    private  ArrayList<String> splitStringUsingRegex( String regex, String tags )
    {
        Pattern pp = Pattern.compile(regex);
        String[] result = pp.split(tags.trim());

        ArrayList<String>   items = new ArrayList<>(Arrays.asList(result));
        
        return items;
    }
}