public void GetAverage_GetAverageUsingMachineId_ReturnTrue()
{
Machine machine = new Machine()
{
MachineId = "IDX147",
MachineName = "Machine147"
};
MachineManager machineMgr = new MachineManager();
machineMgr.CreateMachine(machine: machine);
machineMgr.AddUnits(120, machine.MachineId);
machineMgr.AddUnits(150, machine.MachineId);
int?avg = machineMgr.GetAverage(machine.MachineId);
Assert.IsTrue(avg != null && avg == 135);
}