public function testAppendChild()
{
$node = new Node();
$node->appendChild($a = new A());
$b = new B($node);
$node->prependChild($c = new C());
$node->appendChild($d = new D());
$this->assertEquals(1, $a->getIndex());
$this->assertEquals(2, $b->getIndex());
$this->assertEquals(0, $c->getIndex());
$this->assertEquals(3, $d->getIndex());
$this->assertInstanceOf(A::class, $node->getChildAt(1));
$this->assertInstanceOf(B::class, $node->getChildAt(2));
$this->assertInstanceOf(C::class, $node->getChildAt(0));
$this->assertInstanceOf(D::class, $node->getChildAt(3));
}
