if (md == null) {
            throw new MetadataResolutionException(
                    "treenode without metadata, parent: " + (parent == null ? "null" : parent.toString()));
        }

        return md.groupId + ":" + md.artifactId;
    }

    // ------------------------------------------------------------------------
    public boolean hasChildren() {
        return children != null;
    }

        return createArtifact("org.apache.maven", artifactId, version, type);
    }

    protected Artifact createArtifact(String groupId, String artifactId, String version, String type) throws Exception {
        Artifact a = artifactFactory.createBuildArtifact(groupId, artifactId, version, type);

        return a;
    }

    protected void deleteLocalArtifact(Artifact artifact) throws Exception {

        },
        {
          "group": "com.google.code.findbugs",
          "module": "jsr305",
          "version": {
            "requires": "${jsr305.version}"
          }
        },
        {
          "group": "org.checkerframework",
          "module": "checker-qual",
          "version": {
            "requires": "${checker.version}"
          }
        },
        {
          "group": "com.google.errorprone",

        assertThat(merged.getContributors(), contains(contributor));
    }

    @Test
    void mergeSameDependencies() {
        Dependency dependency = Dependency.newBuilder()
                .groupId("groupId")
                .artifactId("artifactId")
                .type("type")
                .build();

        Model target =
                Model.newBuilder().dependencies(Arrays.asList(dependency)).build();

 * followed by <dfn>flattening</dfn> and <dfn>resolution</dfn>.
 * The version selection is done for each dependency during the collection phase.
 * The flatten phase will keep only a single version per ({@code groupId}, {@code artifactId}) pair.
 * The resolution will actually download the dependencies (or artifacts) that have been computed.
 *
 * @since 4.0.0
 */
@Experimental
@Immutable

      <codeSegments>
        <codeSegment>
          <version>2.0.0+</version>
          <code><![CDATA[
    public String getPluginLookupKey() {
        return groupId + ":" + artifactId;
    }

    public String getId() {
        return groupId + ":" + artifactId + ":" + version;
    }

          ]]></code>
        </codeSegment>
      </codeSegments>
    </class>

        }
        return result.getRawModel();
    }

    /**
     * Gets the identifier of the POM whose effective model could not be built. The general format of the identifier is
     * {@code <groupId>:<artifactId>:<version>} but some of these coordinates may still be unknown at the point the
     * exception is thrown so this information is merely meant to assist the user.
     *

        source.setGroupId("source-group");
        source.setVersion("2.0");
        assertFalse(target.merge(source));
        assertEquals("myArtifact", target.getArtifactId());
        assertEquals("myGroup", target.getGroupId());
        assertEquals("1.0-SNAPSHOT", target.getVersion());
    }
    /*--- END test common metadata ---*/

    /*--- START test "groupId/artifactId/version" metadata ---*/
    @Test

        packagingRegistry = emptyPackagingRegistry;
    }

    private static Plugin newPlugin(String artifactId, String... goals) {
        return Plugin.newBuilder()
                .groupId("org.apache.maven.plugins")
                .artifactId(artifactId)
                .executions(Arrays.stream(goals)
                        .map(goal -> PluginExecution.newBuilder()

 * </p>
 *
 * @since 4.0.0
 */
@Experimental
@Immutable
public interface Artifact {
    /**
     * {@return a unique identifier for this artifact}
     * The identifier is composed of groupId, artifactId, extension, classifier, and version.
     *
     * @see ArtifactCoordinates#getId()
     */
    @Nonnull
    default String key() {
        String c = getClassifier();
        return getGroupId()