public function testGetHeight()
{
$root = new Node();
$root->addChild($child1 = new Node('child1'))->addChild($child2 = new Node('child2'))->addChild($child3 = new Node('child3'));
$child3->addChild(new Node("a"))->addChild(new Node("b"));
$this->assertEquals(0, $child1->getHeight());
$this->assertEquals(2, $root->getHeight());
$this->assertEquals(1, $child3->getHeight());
}
