validator.validate(settings, problems);
        assertEquals(1, problems.messages.size());
        assertContains(
                problems.messages.get(0), "'servers.server.id' must be unique but found duplicate server with id test");
    }

    @Test
    void testValidateUniqueProfileId() throws Exception {
        Settings settings = new Settings();
        Profile profile1 = new Profile();

 *
 * @since 4.0.0
 */
@Experimental
@Immutable
public interface Artifact {

    /**
     * Returns a unique identifier for this artifact.
     * The identifier is composed of groupId, artifactId, extension, classifier, and version.
     *
     * @return the unique identifier
     */
    @Nonnull
    default String key() {
        return getGroupId()
                + ':'

                () -> buildPom("unique-repo-id/artifact-repo"),
                "Non-unique repository ids did not cause validation error");
    }

    /* MNG-4193 */
    @Test
    void testValidationErrorUponNonUniquePluginRepositoryId() throws Exception {
        assertThrows(
                ProjectBuildingException.class,
                () -> buildPom("unique-repo-id/plugin-repo"),

    String CLEAN = "clean";

    String DEFAULT = "default";

    String SITE = "site";

    String WRAPPER = "wrapper";

    /**
     * Name or identifier of this lifecycle.
     *
     * @return the unique identifier for this lifecycle
     */
    @Override
    String id();

    /**
     * Collection of phases for this lifecycle
     */
    Collection<Phase> phases();

    /**

       declaration is required.

   - [name] tells maven what the user-friendly name of this project is. The name
       element is similar to artifactId in that it is a unique descriptor for

            }
        }

        /*
         * NOTE: This is primarily to keep backward-compat with Maven 2.x which did not validate that dependencies are
         * unique within a single POM. Upon multiple declarations, 2.x just kept the last one but retained the order of
         * the first occurrence. So when we're in lenient/compat mode, we have to deal with such broken POMs and mimic

    }

    /**
     * Create a remote deployment repository.
     *
     * @param id            the unique identifier of the repository
     * @param url           the URL of the repository
     * @param layout        the layout of the repository
     * @param uniqueVersion whether to assign each snapshot a unique version
     */

 * processing by providing a means to transport information that cannot be (easily) extracted from the model itself.
 */
record ModelData(ModelSource source, Model model) {

    /**
     * Gets unique identifier of the model
     *
     * @return The effective identifier of the model, never {@code null}.
     */
    public String id() {

            return null;
        }
        return sources.stream()
                .reduce((a, b) -> {
                    throw new IllegalStateException(String.format(
                            "No unique Source for %s:%s: %s and %s",
                            groupId, artifactId, a.getLocation(), b.getLocation()));
                })
                .orElse(null);
    }

    /**
     * The extension of the artifact.
     *
     * @return the extension or an empty string if none, never {@code null}
     */
    @Nonnull
    String getExtension();

    /**
     * Unique id identifying this artifact
     */
    @Nonnull
    default String getId() {
        return getGroupId()
                + ":" + getArtifactId()
                + ":" + getExtension()