Controller Code:

public with sharing class ExportTemplateController {
    
    public String xlsHeader{
        get{
            String strHeader = '';
            strHeader += '<?xml version="1.0"?>';
            strHeader += '<?mso-application progid="Excel.Sheet"?>';
            return strHeader;
        }
    }
    
    public String filterNameData{
        get{
            String selectedFilterId = this.controller.getFilterId();
            return selectedFilterId;
        }
    }
    
    ApexPages.StandardSetController controller;    
    public ExportCSVController(ApexPages.StandardSetController controller) {
        
        this.controller = controller;   
        if (controller.getResultSize() < 2000 ) {
            controller.setPageSize(controller.getResultSize());
        } else {
            controller.setPageSize(2000);
        }
   }

Test Class (so far I've researched and written)
 

@isTest
private static void ExportTemplateTest() {

    //Try insert a list of accounts to use Account Controller

    List<Account> testAccs = new List<Account>();
    for (Integer i = 0; i < 200; i++) {
        Account a = new Account(Name='TestAccount' + i);
        testAccs.add(a);
    }
    insert testAccs;
    
    Test.startTest();
    PageReference pageRef = Page.OpenAccountPage;
    Test.setCurrentPage(pageRef);
    ApexPages.StandardSetController stdSetController = new 
    ApexPages.StandardSetController(testAccs);
    stdSetController.setSelected(testAccs);
    ExportCSVController ext = new ExportCSVController(stdSetController);
    System.assertEquals(200, 200);
    Test.stopTest();
}

The code coverage is now 30%. Please help me with writing methods to cover public String xlsHeader & public String filterNameData.

The Controller was written by another Developer that is no longer working in my company. I'm taking his task now. 

As I've researched, Get is a Read-only variable. How do we call/invoke/access it in Test Class?

Thank you so much.

Controller Code:

public with sharing class ExportTemplateController {
    
    public String xlsHeader{
        get{
            String strHeader = '';
            strHeader += '<?xml version="1.0"?>';
            strHeader += '<?mso-application progid="Excel.Sheet"?>';
            return strHeader;
        }
    }
    
    public String filterNameData{
        get{
            String selectedFilterId = this.controller.getFilterId();
            return selectedFilterId;
        }
    }
    
    ApexPages.StandardSetController controller;    
    public ExportCSVController(ApexPages.StandardSetController controller) {
        
        this.controller = controller;   
        if (controller.getResultSize() < 2000 ) {
            controller.setPageSize(controller.getResultSize());
        } else {
            controller.setPageSize(2000);
        }
   }

Test Class (so far I've researched and written)
 

@isTest
private static void ExportTemplateTest() {

    //Try insert a list of accounts to use Account Controller

    List<Account> testAccs = new List<Account>();
    for (Integer i = 0; i < 200; i++) {
        Account a = new Account(Name='TestAccount' + i);
        testAccs.add(a);
    }
    insert testAccs;
    
    Test.startTest();
    PageReference pageRef = Page.OpenAccountPage;
    Test.setCurrentPage(pageRef);
    ApexPages.StandardSetController stdSetController = new 
    ApexPages.StandardSetController(testAccs);
    stdSetController.setSelected(testAccs);
    ExportCSVController ext = new ExportCSVController(stdSetController);
    System.assertEquals(200, 200);
    Test.stopTest();
}

The code coverage is now 30%. Please help me with writing methods to cover public String xlsHeader & public String filterNameData.

The Controller was written by another Developer that is no longer working in my company. I'm taking his task now. 

As I've researched, Get is a Read-only variable. How do we call/invoke/access it in Test Class?

Thank you so much.