@Nonnull
    <T> T lookup(Class<T> type, String name);

    /**
     * Performs a lookup for optional typed component.
     *
     * @param type The component type.
     * @return Optional carrying component or empty optional if no such component.
     * @param <T> The component type.
     * @throws LookupException if there is some provisioning related issue.
     */
    @Nonnull
    <T> Optional<T> lookupOptional(Class<T> type);

    private void validateIdentity() {
        if (empty(groupId)) {
            throw new InvalidArtifactRTException(
                    groupId, artifactId, getVersion(), type, "The groupId cannot be empty.");
        }

        if (artifactId == null) {
            throw new InvalidArtifactRTException(
                    groupId, artifactId, getVersion(), type, "The artifactId cannot be empty.");
        }

    default Optional<Version> getLowerVersion() {
        return getVersions().isEmpty()
                ? Optional.empty()
                : Optional.of(getVersions().get(0));
    }

    @Nonnull
    default Optional<Version> getHigherVersion() {
        return getVersions().isEmpty()
                ? Optional.empty()
                : Optional.of(getVersions().get(getVersions().size() - 1));
    }

    @Nonnull

import java.util.List;

import org.apache.maven.project.MavenProject;
import org.junit.jupiter.api.Test;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.empty;
import static org.hamcrest.Matchers.is;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNotSame;

/**
 */
class DefaultMavenExecutionTest {

    private static final Attributes.Name AUTO_MODULE_NAME = new Attributes.Name("Automatic-Module-Name");

    /**
     * Module information for the path specified at construction time.
     * This map is usually either empty if no module was found, or a singleton map.
     * It may however contain more than one entry if module hierarchy was detected,
     * in which case there is one key per sub-directory.
     *

    //     * or an empty collection when the location is not set or is invalid.
    //     *
    //     * @return List
    //     */
    //    List getSourceDirectories();
    //
    //    /**
    //     * Returns a {@link java.io.File}s which represent the locations of the Javadoc for this platform,
    //     * or empty collection if the location is not set or invalid
    //     *

import org.junit.jupiter.api.Test;

import static java.util.Collections.singleton;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.containsInAnyOrder;
import static org.hamcrest.Matchers.empty;
import static org.hamcrest.Matchers.is;

class DefaultBuildResumptionDataRepositoryTest {
    private final DefaultBuildResumptionDataRepository repository = new DefaultBuildResumptionDataRepository();

    @Test

  <name>Maven Integration Test :: MNG-3979</name>
  <description>
    Test that during inheritance the merging/joining of subtrees with equal identifier doesn't crash if the parent
    POM has a non-empty element and the child POM has an empty element to join.
  </description>

  <properties/>

  <repositories>
    <repository>
      <id>equal-repo-id</id>
      <url>file:///${basedir}/null</url>
      <snapshots/>

need it so that empty directory does not get deleted...

        if (Files.isDirectory(pomPath)) {
            pomPath = context.locate(pomPath);
        }

        if (pomPath == null || !Files.isRegularFile(pomPath)) {
            return Optional.empty();
        }

        Optional<RelativeProject> mappedProject = Optional.ofNullable(context.getRawModel(pomFile, pomPath.normalize()))
                .map(BuildModelTransformer::toRelativeProject);