public void TestRevert()
{
//Arrange
TankHistory history = new TankHistory();
FuelTank tank = new FuelTank()
{
FuelLevel = 100, FuelType = "Unleaded"
};
//act
history.memento = tank.CreateMemento();
tank.FuelLevel = 150;
tank.FuelType = "Diesel";
tank.RevertTank(history.memento);
//assert
Assert.AreEqual(100, tank.FuelLevel);
Assert.AreEqual("Unleaded", tank.FuelType);
}