EclipseModel eclipse = project.getExtensions().getByType(EclipseModel.class);
        eclipse.getClasspath().setSourceSets(Arrays.asList(testSourceSet));
        eclipse.getClasspath()
            .setPlusConfigurations(
                Arrays.asList(project.getConfigurations().getByName(JavaPlugin.TEST_RUNTIME_CLASSPATH_CONFIGURATION_NAME))
            );

        IdeaModel idea = project.getExtensions().getByType(IdeaModel.class);