MutableGraph<Integer> g2 = createGraph(oppositeType(edgeType));
    g2.putEdge(N1, N2);

    assertThat(graph).isNotEqualTo(g2);
  }

  // Node/edge sets and node/edge connections are the same, but directedness differs.
  @Test
  public void equivalent_selfLoop_directedVsUndirected() {
    graph.putEdge(N1, N1);

    MutableGraph<Integer> g2 = createGraph(oppositeType(edgeType));
    g2.putEdge(N1, N1);

    MutableGraph<Integer> g2 = createGraph(oppositeType(edgeType));
    g2.putEdge(N1, N2);

    assertThat(graph).isNotEqualTo(g2);
  }

  // Node/edge sets and node/edge connections are the same, but directedness differs.
  @Test
  public void equivalent_selfLoop_directedVsUndirected() {
    graph.putEdge(N1, N1);

    MutableGraph<Integer> g2 = createGraph(oppositeType(edgeType));
    g2.putEdge(N1, N1);

      case DIRECTED:
        return NetworkBuilder.directed().allowsSelfLoops(true).build();
    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  private static EdgeType oppositeType(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return EdgeType.DIRECTED;
      case DIRECTED:
        return EdgeType.UNDIRECTED;
    }

      case DIRECTED:
        return NetworkBuilder.directed().allowsSelfLoops(true).build();
    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  private static EdgeType oppositeType(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return EdgeType.DIRECTED;
      case DIRECTED:
        return EdgeType.UNDIRECTED;
    }