protected static void Degree_Test(
[NotNull] IMutableBidirectionalGraph <int, Edge <int> > graph)
{
var edge1 = new Edge <int>(1, 2);
var edge2 = new Edge <int>(1, 3);
var edge3 = new Edge <int>(1, 4);
var edge4 = new Edge <int>(2, 4);
var edge5 = new Edge <int>(3, 2);
var edge6 = new Edge <int>(3, 3);
graph.AddVerticesAndEdgeRange(new[] { edge1, edge2, edge3, edge4, edge5, edge6 });
graph.AddVertex(5);
Assert.AreEqual(3, graph.Degree(1));
Assert.AreEqual(3, graph.Degree(2));
Assert.AreEqual(4, graph.Degree(3)); // Self edge
Assert.AreEqual(2, graph.Degree(4));
Assert.AreEqual(0, graph.Degree(5));
}