assertEquals(
                RootLocator.UNABLE_TO_FIND_ROOT_PROJECT_MESSAGE,
                assertThrows(IllegalStateException.class, session::getRootDirectory)
                        .getMessage());
    }

    @Test
    void testRootDirectory() {
        RepositorySystemSession rss = new DefaultRepositorySystemSession(h -> false);

     * containing the {@code .mvn} directory or flagged with {@code root="true"}.
     *
     * @throws IllegalStateException if the root directory could not be found
     * @see Session#getRootDirectory()
     */
    @Nonnull
    Path getRootDirectory();

    /**
     * Returns project parent project, if any.
     */
    @Nonnull
    Optional<Project> getParent();

    }

    @Override
    public boolean isRootProject() {
        return getBasedir().equals(getRootDirectory());
    }

    @Override
    public Path getRootDirectory() {
        return project.getRootDirectory();
    }

    @Override
    public Optional<Project> getParent() {
        MavenProject parent = project.getParent();

    @Override
    public Instant getStartTime() {
        return getMavenSession().getRequest().getStartTime().toInstant();
    }

    @Override
    public Path getRootDirectory() {
        return getMavenSession().getRequest().getRootDirectory();
    }

    @Override
    public Path getTopDirectory() {
        return getMavenSession().getRequest().getTopDirectory();
    }

    @Nonnull
    @Override

     */
    public Path getTopDirectory() {
        return request.getTopDirectory();
    }

    /**
     * @see MavenExecutionRequest#getRootDirectory()
     * @since 4.0.0
     */
    public Path getRootDirectory() {
        return request.getRootDirectory();
    }

    public MavenExecutionRequest getRequest() {
        return request;
    }

     * @deprecated use {@link #setRootDirectory(Path)} instead
     */
    @Deprecated
    void setMultiModuleProjectDirectory(File file);

    /**
     * @since 3.3.0
     * @deprecated use {@link #getRootDirectory()} instead
     */
    @Deprecated
    File getMultiModuleProjectDirectory();

    /**
     * Sets the top directory of the project.
     *
     * @since 4.0.0
     */

                }
            }

            private void doLoadFullReactor() {
                Path rootDirectory;
                try {
                    rootDirectory = request.getSession().getRootDirectory();
                } catch (IllegalStateException e) {
                    // if no root directory, bail out
                    return;
                }
                List<Path> toLoad = new ArrayList<>();

            return startTime;
        }

        @Override
        public Path getTopDirectory() {
            return null;
        }

        @Override
        public Path getRootDirectory() {
            return null;
        }

        @Override
        public List<Project> getProjects() {
            return List.of();
        }

        @Override

     *
     * @throws IllegalStateException if the root directory could not be found
     * @see #getTopDirectory()
     * @see Project#getRootDirectory()
     */
    @Nonnull
    Path getRootDirectory();

    @Nonnull
    List<Project> getProjects();

    /**
     * Returns the plugin context for mojo being executed and the specified

    }

    @Deprecated
    @Override
    public File getMultiModuleProjectDirectory() {
        return multiModuleProjectDirectory;
    }

    @Override
    public Path getRootDirectory() {
        if (rootDirectory == null) {
            throw new IllegalStateException(RootLocator.UNABLE_TO_FIND_ROOT_PROJECT_MESSAGE);
        }
        return rootDirectory;
    }

    @Override