public void HyperGraph_AddEdge_has_to_work()
        {
            HyperGraph hyperGraph = new HyperGraph();

            Assert.ThrowsException <ArgumentException>(() => { hyperGraph.AddEdge("00", "00", "00"); }, "This graph does not conatin a vertex with value '00'.");

            Vertex    v1 = hyperGraph.AddVertex("00");
            HyperEdge h1 = hyperGraph.AddEdge("00", "00", "00");

            Assert.AreEqual(3, h1.VertexCount());
            Assert.IsTrue(h1.ContainsOnVertexBasis(v1));

            HyperEdge h2 = new HyperEdge("00", "01", "10");

            Assert.ThrowsException <ArgumentException>(() => { hyperGraph.AddEdge(new Vertex("00"), new Vertex("01"), new Vertex("10")); }, $"This graph does not conatin a vertex with value '01'");

            Vertex v2 = hyperGraph.AddVertex("11");
            Vertex v3 = hyperGraph.AddVertex("01");
            Vertex v4 = hyperGraph.AddVertex("10");

            Assert.ThrowsException <ArgumentException>(() => hyperGraph.AddEdge(v2, v2, v2), "Vertices must not be equal.");
            HyperEdge h3 = hyperGraph.AddEdge(v1, v3, v4);

            Assert.IsTrue(h3.ContainsOnVertexBasis(v1));
            Assert.IsTrue(h3.ContainsOnVertexBasis(v3));
            Assert.IsTrue(h3.ContainsOnVertexBasis(v4));

            Assert.IsFalse(h3.ContainsOnEdgeBasis(v1));
            Assert.IsFalse(h3.ContainsOnEdgeBasis(v3));
            Assert.IsFalse(h3.ContainsOnEdgeBasis(v4));

            HyperEdge h4 = new HyperEdge(new Vertex("00"), new Vertex("01"), new Vertex("10"));

            Assert.IsTrue(hyperGraph.HasEdge(h4));
            Assert.ThrowsException <ArgumentException>(() => { hyperGraph.AddEdge(new Vertex("00"), new Vertex("01"), new Vertex("10")); }, $"This Graph has already an edge '-00-01-10->'.");
            Assert.ThrowsException <ArgumentException>(() => { hyperGraph.AddEdge("00", "01", "10"); }, $"This Graph has already an edge '-00-01-10->'.");
        }