public void HeadTest()
{
var stack = CustomStack <string> .Cons("Hello", CustomStack <string> .Empty);
var head = CustomStack <string> .Head(stack);
Assert.AreEqual("Hello", head);
}
public void EmptyHeadTest()
{
var stack = CustomStack <string> .Empty;
AssertThrows <ArgumentNullException>(() => CustomStack <string> .Head(stack));
}
