TEST(List, can_delete_first_element) {
	List<int> list;
	list.AddToHead(1);
	list.AddToTail(4);
	list.DeleteFirst();

	EXPECT_EQ(1, list.GetLength());
	EXPECT_EQ(4, list.GetHead()->GetVar());

}
TEST(List, can_delete_single_element)
{
	List<int> list;
	list.AddToHead(1);
	list.DeleteFirst();

	EXPECT_EQ(0, list.GetLength());
	EXPECT_EQ(NULL, list.GetHead());

}