Application\Controller\IndexController::indexAction PHP Method

    public function indexAction()
    {
        if (class_exists(AdminModule::class, false)) {
            return $this->redirect()->toRoute('zf-apigility/ui');
        }
        return new ViewModel();
    }

 public function testIndexActionReturnsViewModel()
 {
     $controller = new IndexController();
     $this->assertInstanceOf(ViewModel::class, $controller->indexAction());
 }