here is the controller extension code

public class ext_PartnerPositionProposal {

private Partner_Position_Draft__c PPD = new Partner_Position_Draft__c();

    public ext_PartnerPositionProposal(ApexPages.StandardController controller) {
        PPD = (Partner_Position_Draft__c)controller.getRecord();
    }
    
    public PageReference submit()
    {        
        // Change Stage
        PPD.Status__c = 'submitted';
        //Controller.save();
        ApexPages.StandardController controller = new ApexPages.StandardController(PPD);
        controller.save();
        //logic to save your data
        PageReference p = new PageReference('http://www.broadcenter.org/Updated.html');
        p.setRedirect(true);
        return p;            
    }
    
           static testMethod void test_ext_PartnerPositionProposal() {
                //Test converage for the myPage visualforce page
                
                PageReference pageRef = Page.PartnerPositionProposal;           
                Test.setCurrentPageReference(pageRef);
                
                // Verify that page fails without parameters 
            System.assertNotEquals('/apex/failure?error=noParam', pageRef.getUrl());
            
                Partner_Position_Draft__c myPPD = [Select Id,Status__c 
                From Partner_Position_Draft__c Limit 1];
                
                ApexPages.StandardController ppd = new ApexPages.standardController(myPPD);
                
                // create an instance of the controller
                
                ext_PartnerPositionProposal PPP  = new ext_PartnerPositionProposal(ppd);                
                PPP.submit();   
                
                }        
    
}