assertThat(edges).doesNotContain(EndpointPair.unordered(N2, N2)); // edge not present
    assertThat(edges).doesNotContain(EndpointPair.unordered(N3, N4)); // nodes not in graph
  }

  @Test
  public void endpointPair_directed_contains() {
    MutableGraph<Integer> directedGraph = GraphBuilder.directed().allowsSelfLoops(true).build();
    directedGraph.putEdge(N1, N1);
    directedGraph.putEdge(N1, N2);