public void TestPeekEmpty()
{
StackUp <string> stack = new StackUp <string>();
Assert.AreEqual(0, stack.Count);
stack.Peek();
}
public void TestPeek()
{
StackUp <string> stack = new StackUp <string>();
stack.Push("Peek");
string s = stack.Peek();
Assert.AreEqual("Peek", s);
}