Hi, how to write test class for vf component Apex class?  
can anyone guide me?
Apex class:
public class salarydetail{
   public static list<Salary_Detail__c>salary; 
    //salary = new list<Salary_Detail__c>();
   public String salaryId {
        get{
            if(salaryId == null && ApexPages.currentPage().getParameters().get('id') != null){
                salaryId = ApexPages.currentPage().getParameters().get('id');
            }
            return salaryId;
        }
        set;
    }
      
    public Salary_Detail__c sd {
       
        get{
            return [SELECT Id, Employee_ID__c,Date_of_Joining__c,Department__c,Designation__c,
                    Gender__c,Location__c,Pan_Number__c,Professional_Tax__c,UAN_No__c,BasicAllowance__c,HouseRentAllowance__c,MonthDays__c,Number_of_Days_present__c, Account_No__c,
                    Skill_up_Allowance__c,PF__c,SpecialAllowance__c,TotalEarnings__c,TotalDeductions__c,
                    NetPay__c,In_Words__c FROM Salary_Detail__c WHERE Id = :salaryId LIMIT 1];
        }
        set;
      
    }
}

Test class:
@ IsTest
public class salarydetailtest {
    public static Testmethod void Salary(){
       Test.startTest(); 
       Employee_Information__c E = new Employee_Information__c();
        
        E.Name='Test';
        E.Employee_Last_Name__c ='s';
        E.Employee_ID__c = 'E-1234';
        E.Date_of_Join__c= system.today();
        E.Tax_Regime__c='Old Regime';
        E.Confirmed_CTC__c=1500000;
        insert E;
        
        Employee_Information__c E1 = new Employee_Information__c();
        
        E1.Name='Test1';
        E1.Employee_Last_Name__c ='s';
        E1.Employee_ID__c = 'E-12345';
        E1.Date_of_Join__c= system.today();
        E1.Tax_Regime__c='New Regime';
        E1.Confirmed_CTC__c=1500000;
        insert E1;
        
     List< Salary_Detail__c>lis=    [SELECT Id, Employee_ID__c,Date_of_Joining__c,Department__c,Designation__c,
                    Gender__c,Location__c,Pan_Number__c,Professional_Tax__c,UAN_No__c,BasicAllowance__c,HouseRentAllowance__c,MonthDays__c,Number_of_Days_present__c, Account_No__c,
                    Skill_up_Allowance__c,PF__c,SpecialAllowance__c,TotalEarnings__c,TotalDeductions__c,
                    NetPay__c,In_Words__c FROM Salary_Detail__c ];
       Salary_Detail__c s = new Salary_Detail__c();
       
       // s.Employee_Names__c='Tests';
        s.Employee_First_Name__c='Test';
        s.Employee_Last_Name__c ='s';
        s.RecordTypeId = '0123K0000009lfpQAA';
        s.Record_Status__c='Active';  
        s.Date_of_Joining__c=system.today();
        s.Employee_ID__c = 'E-1234';
        s.Employee_Information__c=E.id;
        s.MonthDays__c=31;
        S.LastMonthLeaves__c=1;
        S.LastMonthLops__c=1;
        s.Worked_days__c=30;
        s.Confirmed_CTC__c=1500000;
        s.Basic_Annual__c=450000;
         s.HRA_Annual__c=180000;
         s.Special_Allowance_Annual__c=809250;
        s.Tax_Regime__c='Old Regime'; 
        s.standard_deduction_monthly__c=4167;
        s.Professional_Tax__c=200;
        s.Medical_Reimbursement_Annual__c=0;
            s.Skill_up_Allowance__c =0;
            s.Company_Medical_Insurance_Contribution__c =0; 
          s.zeroto2_5__c=250000;
           s.X2_5to5__c=250000;
           s.X5to7_5__c=250000;
           s.X7_5to10__c=250000;
            s.X10to12_5__c=250000;
           s.X12_5to15__c=250000;
           s.X15Great__c=0;
            s.TaxExempt__c=0;
        s.TotalDeductions__c=0;
        s.TotalEarnings__c=0;
        s.NetPay__c=0;
        lis.add (s);
        upsert lis;
        
         Salary_Detail__c s1 = new Salary_Detail__c();
       
       // s.Employee_Names__c='Tests';
        s1.Employee_First_Name__c='Test';
        s1.Employee_Last_Name__c ='s';
        s1.RecordTypeId = '0123K0000009lfpQAA';
        s1.Record_Status__c='Active';  
        s1.Date_of_Joining__c=system.today();
        s1.Employee_ID__c = 'E-12345';
        s1.Employee_Information__c=E1.id;
        s1.MonthDays__c=31;
        S1.LastMonthLeaves__c=1;
        S1.LastMonthLops__c=1;
        s1.Worked_days__c=30;
        s1.Confirmed_CTC__c=-1;
        s1.Basic_Annual__c=450000;
        s1.HRA_Annual__c=180000;
         s1.Special_Allowance_Annual__c=809250;
        s1.Tax_Regime__c='Old Regime'; 
        s1.standard_deduction_monthly__c=4167;
        s1.Professional_Tax__c=200;
        s1.Medical_Reimbursement_Annual__c=0;
            s1.Skill_up_Allowance__c =0;
            s1.Company_Medical_Insurance_Contribution__c =0; 
          s1.zeroto2_5__c=250000;
           s1.X2_5to5__c=250000;
           s1.X5to7_5__c=250000;
           s1.X7_5to10__c=250000;
            s1.X10to12_5__c=250000;
           s1.X12_5to15__c=250000;
           s1.X15Great__c=0;
            s1.TaxExempt__c=0;
        s1.TotalDeductions__c=0;
        s1.TotalEarnings__c=0;
        s1.NetPay__c=0;
        lis.add (s1);
        upsert lis;
        
        Leave_Request__c L = new Leave_Request__c();
        L.Approval_Status__c ='Approved';
        L.Employee_ID__c = 'E-1234';
        L.Employee_Name__c=E.id;
        L.Last_Month_LOPs__c=1;
        L.Last_Month_Leaves__c=1;
        insert L;

       
        //salarydetailtest t = new salarydetailtest();
         // salarydetailtest.Salary();
        Test.stopTest();
}

    }

Thanks in advance