assertThat(graphAsMutableGraph.removeEdge(N1, N2)).isFalse();
    assertThat(graph.successors(N1)).isEmpty();
    assertThat(graph.predecessors(N2)).isEmpty();
  }

  @Test
  public void removeEdge_oneOfMany() {
    assume().that(graphIsMutable()).isTrue();

    putEdge(N1, N2);
    putEdge(N1, N3);
    putEdge(N1, N4);
    assertThat(graphAsMutableGraph.removeEdge(N1, N3)).isTrue();

    assertThat(networkAsMutableNetwork.edges()).doesNotContain(E12);
    assertThat(networkAsMutableNetwork.edgesConnecting(N1, N2)).isEmpty();
  }

  @Test
  public void removeEdge_oneOfMany() {
    assume().that(graphIsMutable()).isTrue();

    addEdge(N1, N2, E12);
    addEdge(N1, N3, E13);
    addEdge(N1, N4, E14);
    assertThat(networkAsMutableNetwork.edges()).containsExactly(E12, E13, E14);