/**
   * For documenting collections that support no optional features, such as {@link
   * java.util.Collections#emptySet}
   */
  NONE;

  private final Set<Feature<? super Collection>> implied;

  CollectionFeature(Feature<? super Collection>... implied) {
    this.implied = copyToSet(implied);
  }

  @Override
  public Set<Feature<? super Collection>> getImpliedFeatures() {
    return implied;

    private final Collection<String> scopesToCollectForCurrentProject;

    private final Collection<String> scopesToResolveForCurrentProject;

    private final Collection<String> scopesToCollectForAggregatedProjects;

    private final Collection<String> scopesToResolveForAggregatedProjects;

    private volatile Collection<?> lastDependencyArtifacts = Collections.emptyList();

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.project.artifact;

import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.apache.maven.artifact.Artifact;
import org.apache.maven.artifact.DefaultArtifact;
import org.apache.maven.artifact.InvalidArtifactRTException;

import org.eclipse.aether.RepositorySystem;
import org.eclipse.aether.RepositorySystemSession;
import org.eclipse.aether.collection.DependencyGraphTransformer;
import org.eclipse.aether.collection.DependencyManager;
import org.eclipse.aether.collection.DependencySelector;
import org.eclipse.aether.collection.DependencyTraverser;
import org.eclipse.aether.internal.impl.SimpleLocalRepositoryManagerFactory;

   * </ol>
   *
   * @param collection the presumed-immutable collection
   * @param sampleElement an element of the same type as that contained by {@code collection}.
   *     {@code collection} may or may not have {@code sampleElement} as a member.
   */
  public static <E extends @Nullable Object> void assertCollectionIsUnmodifiable(
      Collection<E> collection, E sampleElement) {
    Collection<E> siblingCollection = new ArrayList<>();

  }

  public void testCopyOf_shortcut_empty() {
    Collection<String> c = ImmutableList.of();
    assertSame(c, ImmutableList.copyOf(c));
  }

  public void testCopyOf_shortcut_singleton() {
    Collection<String> c = ImmutableList.of("a");
    assertSame(c, ImmutableList.copyOf(c));
  }

  public void testCopyOf_shortcut_immutableList() {
    Collection<String> c = ImmutableList.of("a", "b", "c");

  public void testEntrySetEquals() {
    resetContainer(mapEntry(k0(), v0()), mapEntry(k1(), v0()), mapEntry(k0(), v3()));
    Set<Entry<K, Collection<V>>> expected = new HashSet<>();
    expected.add(mapEntry(k0(), (Collection<V>) Lists.newArrayList(v0(), v3())));
    expected.add(mapEntry(k1(), (Collection<V>) Lists.newArrayList(v0())));
    new EqualsTester().addEqualityGroup(expected, multimap().asMap().entrySet()).testEquals();
  }

  public void testEntrySetEquals() {
    resetContainer(mapEntry(k0(), v0()), mapEntry(k1(), v0()), mapEntry(k0(), v3()));
    Set<Entry<K, Collection<V>>> expected = new HashSet<>();
    expected.add(mapEntry(k0(), (Collection<V>) Lists.newArrayList(v0(), v3())));
    expected.add(mapEntry(k1(), (Collection<V>) Lists.newArrayList(v0())));
    new EqualsTester().addEqualityGroup(expected, multimap().asMap().entrySet()).testEquals();
  }

    @Override
    @SuppressWarnings({"unchecked", "rawtypes"}) // needed for arrays
    public Entry<String, Collection<Integer>>[] createArray(int length) {
      return new Entry[length];
    }

    @Override
    public Iterable<Entry<String, Collection<Integer>>> order(
        List<Entry<String, Collection<Integer>>> insertionOrder) {
      return insertionOrder;
    }

    @Override

   * </ol>
   *
   * @param collection the presumed-immutable collection
   * @param sampleElement an element of the same type as that contained by {@code collection}.
   *     {@code collection} may or may not have {@code sampleElement} as a member.
   */
  public static <E extends @Nullable Object> void assertCollectionIsUnmodifiable(
      Collection<E> collection, E sampleElement) {
    Collection<E> siblingCollection = new ArrayList<>();