public void AddFirst_WhenNoItemsInTheList_ShouldBeTheOnlyElement()
{
// Arrange
var linkedList = new SinglyLinkList<int>();
var node = new SinglyLinkListNode<int>(10);
// Act
linkedList.AddFirst(node);
// Assert
Assert.AreEqual(1, linkedList.Count, "There should be only 1 item.");
Assert.AreEqual(1, linkedList.Count(), "Enumeration should return single item.");
Assert.AreEqual(10, linkedList.First(), "The first item that it returns shall we the expected item.");
Assert.IsNotNull(linkedList.GetHeadAndTail().Item1, "Should not be null");
Assert.AreSame(node, linkedList.GetHeadAndTail().Item1, "Head should be referring to the same item.");
Assert.AreSame(node, linkedList.GetHeadAndTail().Item2, "Tail should be referring to the same item.");
}