}

  @Test
  public void incidentEdges_noIncidentEdges() {
    addNode(N1);
    assertThat(graph.incidentEdges(N1)).isEmpty();
  }

  @Test
  public void incidentEdges_nodeNotInGraph() {
    assertNodeNotInGraphErrorMessage(
        assertThrows(IllegalArgumentException.class, () -> graph.incidentEdges(NODE_NOT_IN_GRAPH)));
  }

  @Test
  public void degree_oneEdge() {

  }

  @Test
  public void incidentEdges_isolatedNode() {
    addNode(N1);
    assertThat(network.incidentEdges(N1)).isEmpty();
  }

  @Test
  public void incidentEdges_nodeNotInGraph() {
    assertNodeNotInGraphErrorMessage(
        assertThrows(
            IllegalArgumentException.class, () -> network.incidentEdges(NODE_NOT_IN_GRAPH)));
  }

  @Test