Hi Everyone,
I am new to test classes.I tried all suggestions but stil it shows the same error.


public class fileAttachToMultipleRecordsController{
Public Attachment myfile;
Public String VMfileName{get;set;}
public String ContactIds{get;set;}
public Contact con{get;set;}
public List<Contact> contacts{get;set;}
    
  public fileAttachToMultipleRecordsController(){
    contacts= new List<Contact>();
    con= new Contact();
      }    
   
    Public Attachment getmyfile()
    {
        myfile = new Attachment();
        return myfile;
    }
    
    public fileAttachToMultipleRecordsController(ApexPages.StandardController controller) {
       ContactIds= ApexPages.currentPage().getParameters().get('array');
      }
      
      
    Public Pagereference Savedoc()
    {
      if(ContactIds!= null || ContactIds!= ''){
         List<String> strConIds= ContactIds.split(',');
            for(Id conId:strConIds){
                Attachment a = new Attachment(parentId =conId,name=myfile.name, body = myfile.body);
                insert a;
                VMfileName=a.Name;
         
        Task newTask = new Task(Description = 'Attached a file under the attachment sections',Priority = 'Normal',Subject ='Attached a File'+'-'+VMfileName,Status='Completed',
                                       ActivityDate=System.today(),
                                       whoid=conId);     
                        Insert newTask;
                 }
             }
       PageReference pf=new PageReference('/003/o');
    return pf;
    }   

   
@isTest(SeeAllData=true)
        public static void testfileAttachToMultipleRecordsController(){
 String ContactIds;

           PageReference pr = Page.fileAttachToMultipleRecords;
              test.setCurrentPage(pr);
              fileAttachToMultipleRecordsController ftmr= new fileAttachToMultipleRecordsController();
              ftmr.getmyfile();
              ftmr.Savedoc();
            
              
               Contact c=new Contact();
               c.LastName='Test Name';
               insert c;
               Contact c1=new Contact();
               c1.LastName='Test Name1';
               insert c1;
               
              ApexPages.StandardController controller = new ApexPages.StandardController(c.id);
                Attachment a = new Attachment(parentId =c.id,name='test Name');
                        insert a;
              String VMfileName='test name';
              Task newTask = new Task(Description = 'Attached a file under the attachment sections',Priority = 'Normal',Subject ='Attached a File'+'-'+VMfileName,Status='Completed',
                                       ActivityDate=System.today());
                                            
                        Insert newTask;
                 
              } 

}