public void GetTotal_GetTotalUsingMachineId_ReturnTrue() { Machine machine = new Machine() { MachineId = "IDX147", MachineName = "Machine147" }; MachineManager machineMgr = new MachineManager(); machineMgr.CreateMachine(machine: machine); machineMgr.AddUnits(120, machine.MachineId); int?total = machineMgr.GetTotal(machine.MachineId); Assert.IsTrue(total != null && total == 120); }