public void Push_element_is_on_top_of_the_stack()
{
MyStack <int> stack = new MyStack <int>();
stack.Push(123);
Assert.AreEqual(123, stack.Peak());
}
public void Peak_empty_stack_throw_exception()
{
MyStack <int> stack = new MyStack <int>();
Assert.Catch <InvalidOperationException>(() => stack.Peak());
}
