public function testBelowPlacement()
{
$stack = new ProtocolLayerStack();
$layerA = new \ClientProtocolLayer();
$layerB = new \ClientProtocolLayer();
$layerC = new \ClientProtocolLayer();
$stack->addLayer($layerA, ProtocolLayerStack::PLACEMENT_BELOW);
$stack->addLayer($layerB, ProtocolLayerStack::PLACEMENT_BELOW, $layerA);
$stack->addLayer($layerC, ProtocolLayerStack::PLACEMENT_BELOW, $layerA);
$this->assertEquals(true, $layerB === $stack->getBottomLayer());
$this->assertEquals(true, $layerA === $stack->getTopLayer());
$this->assertEquals(true, $layerC === $layerA->getLowerLayer());
$this->assertEquals(null, $layerA->getUpperLayer());
$this->assertEquals(true, $layerB === $layerC->getLowerLayer());
$this->assertEquals(true, $layerA === $layerC->getUpperLayer());
$this->assertEquals(true, $layerC === $layerB->getUpperLayer());
$this->assertEquals(null, $layerB->getLowerLayer());
}
