class ModernRenderElementTest

class ModernRenderElementTest extends UnitTestCase {
  public function testChildren() : void {
    $factory = $this->createMock(FactoryInterface::class);
    $elementInfoManager = new class ($factory) extends ElementInfoManager {
      public function __construct(protected $factory) {
      }

};
    $factory->expects($this->any())
      ->method('createInstance')
      ->willReturnCallback(fn() => new Textfield([], '', NULL, $elementInfoManager));
    // If the type is not given ::fromRenderable presumes "form" and uses the
    // plugin discovery to find which class provides the form element. This
    // test does not set up discovery so some type must be provided.
    $element = [
      '#type' => 'ignored by the mock factory',
    ];
    $elementObject = $elementInfoManager->fromRenderable($element);
    for ($i = 0; $i <= 2; $i++) {
      $child = [
        '#type' => 'ignored by the mock factory',
        '#test' => $i,
      ];
      $elementObject->addChild("test{$i}", $child);
      // addChild() takes the $child render array by reference and stores a
      // reference to it in the render object. To avoid modifying the
      // previously created render object when reusing the $child variable,
      // unset() it to break the reference before reassigning.
      unset($child);
    }
    foreach ([
      1 => [
        'test0',
        'test1',
        'test2',
      ],
      2 => [
        'test0',
        'test2',
      ],
    ] as $delta => $expectedChildrenKeys) {
      $i = 0;
      foreach ($elementObject->getChildren() as $name => $child) {
        $this->assertSame($name, "test{$i}");
        $this->assertSame($i, $child->test);
        $i += $delta;
      }
      $this->assertSame(Element::children($elementObject->toRenderable()), $expectedChildrenKeys);
      // The first iteration tests removing an existing child. The second
      // iteration tests removing a nonexistent child.
      $elementObject->removeChild('test1');
    }
  }

}