i am trying to test my Controller .One doubt is in using Test.startTet and Test.stopTest().i am checking every method in separate unit test . for example

static testmethod void testEditApiSettings(){
         MirrorTestUtility.getApiSettings();
    Test.startTest();
    MirrorSettingsController ctrl = new MirrorSettingsController();   
  ctrl.setEditApiSettings();
  Test.stopTest();
System.assert(ctrl.editApiSettings,'Method perform to Show Insert view# Not able to set ');
}
static testmethod void testDeleteApiSettings(){
MirrorTestUtility.setUpSettings();
Test.startTest();
MirrorSettingsController ctrl = new MirrorSettingsController();
ctrl.deleteUserSettings();
Test.stopTest();
 GlassUserApiSettings__c userSettings =  GlassUserApiSettings__c.getValues(UserInfo.getUserId());
System.assert(userSettings== null ,'User settings are present ence Method don\'t delete Usetr Settings' );
}

so you can see i create ctrl every time in test.startTest() is this more appropriate or creating it before Test.startTest();

1. there is a DML exception perhaps that cant come because DML limit is 100 and i am hardly using 2-3 in my controller. i write a function

   public PageReference deleteUserSettings(){
   try{  
   delete userSettings;  
   userSettings = GlassUserApiSettings__c.getValues(Userinfo.getUserId());
   }
   catch(System.DmlException e){System.debug(e); }
   return null;
    }

   how to test this should i remove this try catch block (because exception is not expected)??How to test this catch block please guideline .