// Edge direction handled correctly
    assertThat(network.outDegree(N2)).isEqualTo(0);
  }

  @Test
  public void edges_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.edges()).containsExactly(E11);
  }

  @Test
  public void incidentEdges_selfLoop() {

    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.incidentEdges(N1)).containsExactly(E11);
  }

  @Test
  public void incidentNodes_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.incidentNodes(E11).source()).isEqualTo(N1);
    assertThat(network.incidentNodes(E11).target()).isEqualTo(N1);
  }