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();
    assertThrows(UnsupportedOperationException.class, () -> edges.add(E12));

    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();
    assertThrows(UnsupportedOperationException.class, () -> edges.add(E12));

    public ResolutionGroup retrieve(
            Artifact artifact, ArtifactRepository localRepository, List<ArtifactRepository> remoteRepositories) {
        throw new UnsupportedOperationException("Cannot retrieve metadata in this test case");
    }

    public List<ArtifactVersion> retrieveAvailableVersions(

   *
   * @since 12.0
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @GwtIncompatible // NavigableSet
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull
  public final E pollFirst() {
    throw new UnsupportedOperationException();
  }

  /**

    }
  }

  @Override
  public void invalidateAll() {
    throw new UnsupportedOperationException();
  }

  @Override
  public CacheStats stats() {
    throw new UnsupportedOperationException();
  }

  @Override
  public ConcurrentMap<K, V> asMap() {
    throw new UnsupportedOperationException();
  }

  /**

      fail(message);
    } catch (UnsupportedOperationException expected) {
    }
  }

  private void expectReturnsFalseOrThrows(Target target) {
    String message = Platform.format("retainAll(%s) should return false or throw", target);
    try {
      assertFalse(message, collection.retainAll(target.toRetain));
    } catch (UnsupportedOperationException tolerated) {
    }
  }

   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull
  public final Entry<E> pollFirstEntry() {
    throw new UnsupportedOperationException();
  }

  /**

   * the range set that are {@linkplain Range#isConnected(Range) connected} with it. Moreover, if
   * {@code range} is empty, this is a no-op.
   *
   * @throws UnsupportedOperationException if this range set does not support the {@code add}
   *     operation
   */
  void add(Range<C> range);

  /**
   * Removes the specified range from this {@code RangeSet} (optional operation). After this

    }
  }

  public void testKeySet_addNotSupported() {
    for (LoadingCache<Object, Object> cache : caches()) {
      assertThrows(UnsupportedOperationException.class, () -> cache.asMap().keySet().add(1));

      assertThrows(
          UnsupportedOperationException.class, () -> cache.asMap().keySet().addAll(asList(1, 2)));
    }
  }


  public void testKeySet_clear() {

    }
  }

  public void testKeySet_addNotSupported() {
    for (LoadingCache<Object, Object> cache : caches()) {
      assertThrows(UnsupportedOperationException.class, () -> cache.asMap().keySet().add(1));

      assertThrows(
          UnsupportedOperationException.class, () -> cache.asMap().keySet().addAll(asList(1, 2)));
    }
  }


  public void testKeySet_clear() {