public void ExtensionTest()
        {
            var graph = new AdjacencyListGraph(8);

            graph.AddArrow(0, 1);
            graph.AddArrow(1, 2);
            graph.AddArrow(2, 0);
            graph.AddArrow(3, 1);
            graph.AddArrow(3, 2);
            graph.AddArrow(5, 2);
            graph.AddArrow(4, 3);
            graph.AddArrow(3, 4);
            graph.AddArrow(4, 5);
            graph.AddArrow(6, 5);
            graph.AddArrow(5, 6);
            graph.AddArrow(7, 4);

            var result = graph.FindCycles();

            Assert.That(result.Count, Is.EqualTo(1));
            //CollectionAssert.AreEqual(new[] { 0, 1, 2 }, result[0]);
            //CollectionAssert.AreEqual(new[] { 3, 4 }, result[1]);
            //CollectionAssert.AreEqual(new[] { 5, 6 }, result[2]);
        }