.containsExactlyElementsIn(network.edgesConnecting(adjacentNode, node));
      }
    }
  }

  @Override
  @Test
  public void nodes_checkReturnedSetMutability() {
    Set<Integer> nodes = network.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(network.nodes()).containsExactlyElementsIn(nodes);
  }

  @Override
  @Test

            .containsExactlyElementsIn(network.edgesConnecting(adjacentNode, node));
      }
    }
  }

  @Override
  @Test
  public void nodes_checkReturnedSetMutability() {
    Set<Integer> nodes = network.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(network.nodes()).containsExactlyElementsIn(nodes);
  }

  @Override
  @Test

    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = network.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(network.nodes()).containsExactlyElementsIn(nodes);
  }

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

    Set<String> edges = network.edges();

    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = network.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(network.nodes()).containsExactlyElementsIn(nodes);
  }

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

    Set<String> edges = network.edges();

      Set<Object> expected = Maps.newHashMap(cache.asMap()).keySet();
      assertThat(keys).containsExactlyElementsIn(expected);
      assertThat(keys.toArray()).asList().containsExactlyElementsIn(expected);
      assertThat(keys.toArray(new Object[0])).asList().containsExactlyElementsIn(expected);

      new EqualsTester()
          .addEqualityGroup(cache.asMap().keySet(), keys)

      Set<Object> expected = Maps.newHashMap(cache.asMap()).keySet();
      assertThat(keys).containsExactlyElementsIn(expected);
      assertThat(keys.toArray()).asList().containsExactlyElementsIn(expected);
      assertThat(keys.toArray(new Object[0])).asList().containsExactlyElementsIn(expected);

      new EqualsTester()
          .addEqualityGroup(cache.asMap().keySet(), keys)

    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = graph.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(graph.nodes()).containsExactlyElementsIn(nodes);
  }

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

    addNode(N1);

    assertThat(actual.getLowerBounds())
        .asList()
        .containsExactlyElementsIn(asList(expected.getLowerBounds()))
        .inOrder();
    assertThat(actual.getUpperBounds())
        .asList()
        .containsExactlyElementsIn(asList(expected.getUpperBounds()))
        .inOrder();
  }

  private static class WithTypeVariable {

    assertThat(actual.getLowerBounds())
        .asList()
        .containsExactlyElementsIn(asList(expected.getLowerBounds()))
        .inOrder();
    assertThat(actual.getUpperBounds())
        .asList()
        .containsExactlyElementsIn(asList(expected.getUpperBounds()))
        .inOrder();
  }

  private static class WithTypeVariable {

        List<Integer> target = Lists.newArrayList(contents);
        target.add(4);
        C addThenFilter = filter(createUnfiltered(target), EVEN);

        assertThat(filterThenAdd).containsExactlyElementsIn(addThenFilter);
      }
    }

    public void testAdd() {
      for (List<Integer> contents : SAMPLE_INPUTS) {
        for (int toAdd = 0; toAdd < 10; toAdd++) {