PhpSchool\CliMenu\CliMenuBuilder::addSubMenu PHP Method

    public function addSubMenu($id)
    {
        Assertion::string($id);
        $this->menuItems[] = $id;
        $this->subMenus[$id] = new self($this);
        return $this->subMenus[$id];
    }

 public function testAddSubMenu()
 {
     $builder = new CliMenuBuilder();
     $builder->disableDefaultItems();
     $subMenuBuilder = $builder->addSubMenu('sub-menu');
     $menu = $builder->build();
     $this->checkItems($menu, [['class' => MenuMenuItem::class]]);
     $this->assertInstanceOf(CliMenuBuilder::class, $subMenuBuilder);
     $this->assertNotSame($subMenuBuilder, $builder);
     $this->assertSame($builder, $subMenuBuilder->end());
 }