if (scopesToCollect == null) {
            scopesToCollect = Collections.emptySet();
        }
        if (scopesToResolve == null) {
            scopesToResolve = Collections.emptySet();
        }

        if (scopesToCollect.isEmpty() && scopesToResolve.isEmpty()) {
            return new SetWithResolutionResult(null, new LinkedHashSet<>());
        }

     *
     * @param message The message describing the problem, may be {@code null}.
     * @param severity The severity level of the problem, may be {@code null} to default to
     *            {@link SettingsProblem.Severity#ERROR}.
     * @param source A hint about the source of the problem like a file path, may be {@code null}.
     * @param lineNumber The one-based index of the line containing the problem or {@code -1} if unknown.

                    plugin, session.getCurrentProject().getRemotePluginRepositories(), session.getRepositorySession());

            pluginManager.setupPluginRealm(pluginDescriptor, session, null, null, null);
        } catch (Exception e) {
            throw new PluginManagerException(plugin, e.getMessage(), e);
        }

        ClassLoader oldClassLoader = Thread.currentThread().getContextClassLoader();

     * @return The effective repositories or {@code null} if the input was {@code null}.
     */
    List<ArtifactRepository> getEffectiveRepositories(List<ArtifactRepository> repositories);

    /**
     * Determines the mirror for the specified repository.
     *
     * @param repository The repository to determine the mirror for, must not be {@code null}.

        artifacts.add(new DefaultArtifact("g", "a2", "v", "compile", "jar", "", null));
        artifacts.add(new DefaultArtifact("g", "a3", "v", "compile", "jar", "", null));
        artifacts.add(new DefaultArtifact("g", "a4", "v", "compile", "jar", "", null));

        cache.put(project1, new SetWithResolutionResult(null, artifacts));

        assertArrayEquals(

        if (activation == null) {
            return false;
        }

        ActivationProperty property = activation.getProperty();

        if (property == null) {
            return false;
        }

        String name = property.getName();
        boolean reverseName = false;

        if (name != null && name.startsWith("!")) {
            reverseName = true;

        if (profileActivation != null) {
            Activation activation = new Activation();

            activation.setActiveByDefault(profileActivation.isActiveByDefault());

            activation.setJdk(profileActivation.getJdk());

            org.apache.maven.profiles.ActivationProperty profileProp = profileActivation.getProperty();

            if (profileProp != null) {

     *
     * @param groupId The group identifier of the POM, must not be {@code null}.
     * @param artifactId The artifact identifier of the POM, must not be {@code null}.
     * @param version The version of the POM, must not be {@code null}.
     * @return The source of the requested POM, never {@code null}.
     * @throws UnresolvableModelException If the POM could not be resolved from any configured repository.
     */

     *
     * @return The global toolchains source or {@code null} if none.
     */
    Source getGlobalToolchainsSource();

    /**
     * Sets the global toolchains source. If both user toolchains and a global toolchains are given, the user toolchains
     * take precedence.
     *
     * @param globalToolchainsSource The global toolchains source, may be {@code null} to disable global toolchains.

    @BeforeEach
    void setUp() throws Exception {
        policy = new DefaultGraphConflictResolutionPolicy();
        e1 = new MetadataGraphEdge("1.1", true, null, null, 2, 1);
        e2 = new MetadataGraphEdge("1.2", true, null, null, 3, 2);
        e3 = new MetadataGraphEdge("1.2", true, null, null, 2, 3);
    }

    // ------------------------------------------------------------------------------------------
    @Test