public void Kopf_ist_immer_gleich()
        {
            var getHead = new GetHead();
            var head    = getHead.Execute(new[] { 7, 7, 7 });

            Assert.AreEqual(head, 7);
        }
        public void Kopf_ist_erstes_Element()
        {
            var getHead = new GetHead();
            var head    = getHead.Execute(new[] { 5, 6, 7 });

            Assert.AreEqual(head, 5);
        }
        public void Kopf_ist_negativ()
        {
            var getHead = new GetHead();
            var head    = getHead.Execute(new[] { -5 });

            Assert.AreEqual(head, -5);
        }