expect:
        replacements.getReplacementFor(newId("com.google.collections", "google-collections")).target == newId("com.google.guava", "guava")
        replacements.getReplacementFor(newId("foo", "bar")).target == newId("foo", "xxx")
        replacements.getReplacementFor(newId("foo", "bar")).reason == 'custom'

        !replacements.getReplacementFor(newId("com.google.guava", "guava"))

        @Nullable
        @Override
        public Replacement getReplacementFor(ModuleIdentifier sourceModule) {
            return null;
        }

        @Override
        public boolean participatesInReplacements(ModuleIdentifier moduleId) {
            return false;
        }
    };

    @Nullable Replacement getReplacementFor(ModuleIdentifier sourceModule);

        if (requested instanceof ModuleComponentSelector) {
            ModuleComponentSelector selector = (ModuleComponentSelector) requested;
            ProjectComponentIdentifier replacement = getReplacementFor(selector);
            if (replacement != null) {
                ProjectComponentSelector targetProject = DefaultProjectComponentSelector.newSelector(
                    replacement,

     */
    @Override
    public PotentialConflict registerCandidate(CandidateModule candidate) {
        ModuleReplacementsData.Replacement replacement = moduleReplacements.getReplacementFor(candidate.getId());
        ModuleIdentifier replacedBy = replacement == null ? null : replacement.getTarget();
        return potentialConflict(conflicts.newElement(candidate.getId(), candidate.getVersions(), replacedBy));

        handler.hasConflicts()
    }

    def "registers module with module conflict"() {
        def a = candidate("org", "a", "1", "2")
        def b = candidate("org", "b", "1")

        replacements.getReplacementFor(DefaultModuleIdentifier.newId("org", "a")) >> new ModuleReplacementsData.Replacement(DefaultModuleIdentifier.newId("org", "b"), null)

        when:
        def aX = handler.registerCandidate(a)

            @Override
            public ModuleIdentifier getReplacedBy() {
                return unwrap(replacements.get(source));
            }
        };
    }

    @Override
    public Replacement getReplacementFor(ModuleIdentifier sourceModule) {
        return replacements.get(sourceModule);
    }

    @Override
    public boolean participatesInReplacements(ModuleIdentifier moduleId) {

        moduleReplacements.participatesInReplacements(moduleA) >> true
        moduleReplacements.participatesInReplacements(moduleB) >> true
        moduleReplacements.getReplacementFor(moduleA) >> new ModuleReplacementsData.Replacement(moduleB, null)
        1 * conflictResolver.select(!null) >> {  args ->
            def details = args[0]