*
     * <strong>Note that late changes to default test directories may NOT be reflected in this collection and {@link #getTestSources()} should be preferred.</strong>
     *
     * For example see docs for {@link IdeaModule}
     *
     * <strong>This field is {@code @Deprecated}, please use {@link #getTestSources()} instead.</strong>
     */
    @Deprecated
    public Set<File> getTestSourceDirs() {
        return testSourceDirs;

        return sourceFiles("app/views");
    }

    List<SourceFile> getConfSources() {
        return sourceFiles("conf", "shared") + sourceFiles("conf")
    }

    List<SourceFile> getTestSources() {
        return sourceFiles("test")
    }

    List<SourceFile> getOtherSources() {
        return [ sourceFile("", "README", "shared") ]
    }

        buildFile << """
        ${registerCustomLanguage()}

        @Managed
        interface BuildType {
            ModelMap<CustomSourceSet> getComponentSources()
            ModelSet<CustomSourceSet> getTestSources()
        }

        class Rules extends RuleSource {
            @Model
            void buildType(BuildType buildType) { }

            @Mutate
            void addSources(BuildType buildType){

            .setSourceDirectories(buildSourceDirectories(ideaModule.getSourceDirs(), ideaModule.getGeneratedSourceDirs()))
            .setTestDirectories(buildSourceDirectories(ideaModule.getTestSources().getFiles(), ideaModule.getGeneratedSourceDirs()))
            .setResourceDirectories(buildSourceDirectories(ideaModule.getResourceDirs(), ideaModule.getGeneratedSourceDirs()))

        apply plugin: 'language-base'

        @Managed
        interface BuildType {
            ModelMap<FunctionalSourceSet> getComponentSources()
            ModelSet<FunctionalSourceSet> getTestSources()
        }

        class Rules extends RuleSource {
            @Model
            void buildType(BuildType buildType) { }

            @Mutate
            void addSources(BuildType buildType){

        final IdeaModule ideaModule = ideaModelFor(project).getModule();
        testing.getSuites().withType(JvmTestSuite.class).configureEach(suite -> {
            ideaModule.getTestSources().from(suite.getSources().getAllJava().getSourceDirectories());
            ideaModule.getTestResources().from(suite.getSources().getResources().getSourceDirectories());
        });
    }

==== Replacement collections in `org.gradle.plugins.ide.idea.model.IdeaModule`

The `testResourcesDirs` and `testSourcesDirs` fields and their getters and setters have been deprecated.
Replace usages with the now stable `getTestSources()` and `getTestResources()` methods and their respective setters.
These new methods return and are backed by `ConfigurableFileCollection` instances for improved flexibility of use.