supplier.get(), "use Optional.orNull() instead of a Supplier that returns null");
  }

  @Override
  public @Nullable T orNull() {
    return null;
  }

  @Override
  public Set<T> asSet() {
    return Collections.emptySet();
  }

  @Override
  public <V> Optional<V> transform(Function<? super T, V> function) {
    checkNotNull(function);
    return Optional.absent();
  }

  @Override

  public T or(Supplier<? extends T> supplier) {
    checkNotNull(supplier);
    return reference;
  }

  @Override
  public T orNull() {
    return reference;
  }

  @Override
  public Set<T> asSet() {
    return Collections.singleton(reference);
  }

  @Override
  public <V> Optional<V> transform(Function<? super T, V> function) {
    return new Present<>(
        checkNotNull(

        assertNotNull(set, "No artifacts");
        assertFalse(set.isEmpty(), "No Artifacts");
        assertTrue(set.size() == 3, "Set size should be 3, is " + set.size());

        for (Object aSet : set) {
            Artifact artifact = (Artifact) aSet;
            System.out.println("Artifact: " + artifact.getDependencyConflictId() + " " + artifact.getVersion()
                    + " Optional=" + (artifact.isOptional() ? "true" : "false"));

        Set set = project1.getArtifacts();
        assertNotNull(set, "No artifacts");
        assertFalse(set.isEmpty(), "No Artifacts");

        for (Object aSet : set) {
            Artifact artifact = (Artifact) aSet;
            System.out.println("Artifact: " + artifact.getDependencyConflictId() + " " + artifact.getVersion()
                    + " Scope: " + artifact.getScope());
            assertTrue(

        assertNotNull(set, "No artifacts");
        assertFalse(set.isEmpty(), "No Artifacts");
        assertTrue(set.size() == 3, "Set size should be 3, is " + set.size());

        for (Object aSet : set) {
            Artifact artifact = (Artifact) aSet;
            assertFalse(artifact.getArtifactId().equals("t07-d"));
            System.out.println("Artifact: " + artifact.getDependencyConflictId() + " " + artifact.getVersion()