// check if invalid id is accessed ..
        public void is_idInValid_ReturnFalse()
        {
            // Arrange
            BuildingController b = new BuildingController(ID);

            // Act

            // Assert
            Assert.AreNotEqual(b.GetBuildingID(), "John");
        }
        // --> ( L1 R2 ) <--
        // if buildingId is within the constraints -> get it..
        public void is_idValid_ReturnId()
        {
            // Arrange
            BuildingController b = new BuildingController(ID);

            // Act
            string id = b.GetBuildingID();

            // Assert
            Assert.AreEqual(ID, id);
        }