I'm new to salesforce any one please explani how to write test class for extension controller class.In the vf page I show the account details and custom object details.If the user not staisfied the result .they create case and task based on the scenerio I create one extension controller.
here is my Controlle Code:
public class MeetingOverviewExtension {
    public final Account accRec;
    public String issueRadio {get; set;}
    transient public Integer counts {get; set;}
    //public List<Meeting__c> meetingList=new List<Meeting__c>();
     public List<Meeting__c> meetingList {get; set; }
   
    public MeetingOverviewExtension(ApexPages.StandardController controller){
        accRec = (Account)controller.getRecord();
        meetingList=[select id,StartDate__c,EndDate__c,Expected_Close_Date__c,Location__c,
                    Purpose__c,OutCome__c from Meeting__c where AccountMaster__c=: accRec.id];
        system.debug('check'+meetingList.size());
        
       
             counts = (Integer) [select count() from meeting__c where AccountMaster__c=: accRec.id and Expected_Close_Date__c = THIS_MONTH];
        System.debug('outttt'+counts);
    }
    public PageReference submit(){
         Task T = new Task();
         Case cRec=new Case();
        if(issueRadio == 'Yes'){
            system.debug('yesstruee');
       
        T.Type = 'Email';
                 T.Description = 'Reassign the outcome'; 
                T.Subject='Outcome monitoring';
    T.WhatId = accRec.Id; 
           
            cRec.Status='New';
            cRec.Status='Email';
            cRec.AccountId=accRec.Id;
     
            }
        try{
            insert T;
            insert cRec;
            system.debug('Caseid::'+cRec.id);
        }
        catch(System.DmlException e){
            System.debug(e.getMessage());
            return null;
                
        }

          PageReference page = new PageReference('/'+accRec.Id);
        page.setRedirect(true);
        return page;

            }
  
}
Test Class:
@isTest 
public class MeetingOverviewExtensionTest {
    
    static testMethod void testMethod1(){
        
        Account acc=new Account(Name='TestMethod');
         insert acc;
         Opportunity opp=new Opportunity(Name='TestCaseOpp',StageName='Prospecting',CloseDate=system.today());
             insert opp;
         Meeting__c mRec=new Meeting__c(AccountMaster__c=acc.id,OutCome_Flag__c=false);
         insert mRec;
        ApexPages.StandardController sc = new ApexPages.StandardController(acc);
       // sc.setSelected(acc);
        MeetingOverviewExtension testAccPlan = new MeetingOverviewExtension(sc);
        
         Task T = new Task();
        T.Type = 'Email';
                 T.Description = 'Reassign the outcome'; 
                T.Subject='Outcome monitoring';
                    T.WhatId = acc.Id; 
        insert T;
         PageReference pageRef = Page.MeetingOverviewForm;
       // Test.setCurrentPage(pageRef);
          pageRef.getParameters().put('id', String.valueOf(acc.Id));
        Test.setCurrentPage(pageRef);
    
    }
}