### Question:
AttributedGraph extends AbstractBaseGraph<AttributedVertex, AttributedEdge> { public AttributedVertex addVertex(String id) { return addVertex(id, id); } AttributedGraph();  AttributedGraph(boolean collapseDuplicateEdges); AttributedVertex addVertex(String id); AttributedVertex addVertex(String id, String name); @Override AttributedVertex addVertex(); @Override boolean addVertex(AttributedVertex vertex); AttributedEdge addEdge(AttributedVertex source, AttributedVertex target, String edgeId); @Override boolean addEdge(AttributedVertex source, AttributedVertex target, AttributedEdge edge); @Override AttributedEdge addEdge(AttributedVertex source, AttributedVertex target); int getEdgeCount(); int getVertexCount(); AttributedVertex getVertex(String vertexId);  }### Answer:
@Test public void testAddVertex() { AttributedVertex v = graph.addVertex(); assertTrue(graph.containsVertex(v)); assertEquals(1, graph.getVertexCount()); }