assertThat(networkAsMutableNetwork.nodes()).contains(N1);
  }

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

    addNode(N1);
    ImmutableSet<Integer> nodes = ImmutableSet.copyOf(networkAsMutableNetwork.nodes());
    assertFalse(networkAsMutableNetwork.addNode(N1));
    assertThat(networkAsMutableNetwork.nodes()).containsExactlyElementsIn(nodes);
  }

  /**
   * Returns the subgraph of {@code graph} induced by {@code nodes}. This subgraph is a new graph
   * that contains all of the nodes in {@code nodes}, and all of the {@link Graph#edges() edges}
   * from {@code graph} for which both nodes are contained by {@code nodes}.
   *
   * @throws IllegalArgumentException if any element in {@code nodes} is not a node in the graph
   */

  /**
   * Returns the subgraph of {@code graph} induced by {@code nodes}. This subgraph is a new graph
   * that contains all of the nodes in {@code nodes}, and all of the {@link Graph#edges() edges}
   * from {@code graph} for which both nodes are contained by {@code nodes}.
   *
   * @throws IllegalArgumentException if any element in {@code nodes} is not a node in the graph
   */

import javax.crypto.Cipher;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.bouncycastle.crypto.engines.AESEngine;
import org.bouncycastle.crypto.modes.AEADBlockCipher;
import org.bouncycastle.crypto.modes.CCMBlockCipher;
import org.bouncycastle.crypto.params.AEADParameters;
import org.bouncycastle.crypto.params.KeyParameter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

    for (Integer node : graph.nodes()) {
      new EqualsTester()
          .addEqualityGroup(
              graph.predecessors(node), graph.successors(node), graph.adjacentNodes(node))
          .testEquals();
    }
  }

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

    Set<Integer> nodes = graph.nodes();

use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

    // Helper to lookup a message by code using the production arrays
    private static Optional<String> lookupMessage(int code) {
        int[] codes = WinError.WINERR_CODES;
        String[] msgs = WinError.WINERR_MESSAGES;
        for (int i = 0; i < codes.length; i++) {
            if (codes[i] == code) {
                return Optional.of(msgs[i]);
            }
        }
        return Optional.empty();
    }