how to cover aggregate sobject in test class?

public List<AggregateResult> inBudgetList {get;set;}
inBudgetList = [SELECT  
                            Budget_User__r.Name inAEName,
                            Budget_User__c inAeId,
                            Advertiser__r.Name account, 
                            Sum(Amount__c) inBudAmt,
                            Broadcast_Month_Date__c effectiveDate
                            FROM Sales_Budget__c
                            WHERE Old_Budget_User__c = :selectedUserId
                            GROUP BY Budget_User__r.Name, Budget_User__c, Advertiser__r.Name, Broadcast_Month_Date__c
                            ORDER BY Budget_User__r.Name
                           ];
for(AggregateResult inBudItem: inBudgetList){
                transferObj.transferUser = (String)inBudItem.get('inAEName');	    			    		
                transferObj.account = (String)inBudItem.get('account');
                transferObj.transferIn = (Decimal)inBudItem.get('inBudAmt');
                transferObj.transferEffectiveDate = ((Datetime)inBudItem.get('effectiveDate')).format('MMMMM -YYYY');
                transferLogs.add(transferObj);
                transferObj = new transferLogsWrapper();