public void ApplyCommandPlu100Minus50MutiplyBy10DividedBy2_Equal250()
{
User user = new User();
// User presses calculator buttons
user.Compute('+', 100);
user.Compute('-', 50);
user.Compute('*', 10);
user.Compute('/', 2);
Assert.Equal(250, user.GetResult());
// Undo 4 commands
user.Undo(4);
Assert.Equal(0, user.GetResult());
// Redo 3 commands
user.Redo(3);
Assert.Equal(500, user.GetResult());
}