@isTest
private class Rental_Apply_App_CCEmailTest {
    @IsTest()
    static void testMethod1() {
        List<Rental_Apply_App_CCEmail__mdt> columns = [select Category5_F__c, CCEmail__c from Rental_Apply_App_CCEmail__mdt];
        if (columns.size() > 0) {
            Set<String> fieldset = new Set<String>();
            for (Rental_Apply_App_CCEmail__mdt col : columns) {
                Boolean b1 = String.isNotBlank(col.Category5_F__c);
                Boolean b2 = String.isNotBlank(col.CCEmail__c);
                system.assert(b1 && b2, '审批抄送人设置Category5, 抄送邮件的项目为空。');
                fieldset.add(col.CCEmail__c);
            }

            String queryStr = 'select '+ String.join(new List<String>(fieldset), ', ') + ' from Rental_Apply__c limit 1';
            try {
                Database.query(queryStr);
            } catch(Exception ex) {
                system.assert(false, ex);
            }
        }
    }
}