I have modified AgentCOntributionArticleController as follows:

public class AgentContributionArticleController {
    // The constructor must take a ApexPages.KnowledgeArticleVersionStandardController as an argument
    public AgentContributionArticleController(ApexPages.KnowledgeArticleVersionStandardController ctl) {
        SObject article = ctl.getRecord();   
		String sourceId = ctl.getSourceId();
        Case c = [select subject, description from Case where id=:sourceId];
//  I added this code -- begin
        CaseComment cc = [select LastModifiedDate, LastModifiedBy.Id, LastModifiedBy.Name, IsPublished, CreatedDate, CreatedBy.Id, CreatedBy.Name, CommentBody From CaseComment where ParentId = :sourceId order by LastModifiedDate desc limit 1];
        //check article type with if statement
	    if (article instanceof troubleshootingobj__kav){
            System.Debug('in troubleshootingobj__kav if'); 
            String [] all = cc.CommentBody.split(':',-1);
            if (all.size() != 4 ){
                article.put('title','Some instructions go here...');
                article.put('summary','Some instructions go here...');
                article.put('symptom__c','Some instructions go here...');
                article.put('solution__c','Some instructions gohere...');

                }
            else {
                for (Integer i = 0; i < all.size(); i++) {
                    if (i == 0){
                      article.put('title',all.get(i));
                    }
                    else if (i==1){
                      article.put('summary',all.get(1));
                    }
                    else  if (i == 2){
                    article.put('Symptom__c',all.get(2));
                    }
                    else  if (i == 3){
                    article.put('Solution__c',all.get(3));
                    }
                  }
                } 
           }
// I added this code -- end
    article.put('title', 'From Case: '+c.subject);  //this overrides the default behavior of pre-filling the title of the article with the subject of the closed case. 
    article.put('Details__c',c.description);  
              
}

 Can anyone provide some guidance as to how to modify the default test class for the changes I have made?

Here is the default test class. 

public static testMethod void testAgentContributionArticleController() {
String caseSubject = 'my test';
String caseDesc = 'my test description';
Case c = new Case();
c.subject= caseSubject;
c.description = caseDesc;
insert c;
String caseId = c.id;
System.debug('Created Case: ' + caseId);
ApexPages.currentPage().getParameters().put('sourceId', caseId);
ApexPages.currentPage().getParameters().put('sfdc.override', '1');
ApexPages.KnowledgeArticleVersionStandardController ctl =
new ApexPages.KnowledgeArticleVersionStandardController(new FAQ__kav());
new AgentContributionArticleController(ctl);
System.assertEquals(caseId, ctl.getSourceId());
System.assertEquals('From Case: '+caseSubject, ctl.getRecord().get('title'));
System.assertEquals(caseDesc, ctl.getRecord().get('details__c'));
}

 I have been trying to figure it out myself but I have enough on my hands actually writing the code.  Test code makes my head spin...  ANy hints or some direction on this testing, totally appreciated.