public void CreateRole_Null_Test()
{
//get all the roles from the db
List <Role> previousRoles = rolesBL.GetAllRoles().ToList <Role>();
//add a new role to the db
string roleName = null;
rolesBL.AddRole(roleName);
List <Role> expectedRoles = new List <Role>();
expectedRoles.AddRange(previousRoles); //add the previous Roles to the list
List <Role> actualRoles = rolesBL.GetAllRoles().ToList <Role>();
//check if expected roles with the actual roles are equal
AreListsEqual(expectedRoles, actualRoles);
}