public void PushPop()
{
var stack = new StackArray <int>();
stack.Push(1);
stack.Push(2);
stack.Push(3);
stack.Push(4);
stack.Push(5);
Assert.AreEqual("54321", stack.GetValues());
stack.Pop();
Assert.AreEqual("4321", stack.GetValues());
stack.Pop();
Assert.AreEqual("321", stack.GetValues());
}