public function testHasPrevSibling()
{
Table9Peer::doDeleteAll();
$t0 = new Table9();
$t1 = new Table9();
$t1->setTitle('t1')->setLeftValue(1)->setRightValue(6)->save();
$t2 = new Table9();
$t2->setTitle('t2')->setLeftValue(2)->setRightValue(3)->save();
$t3 = new Table9();
$t3->setTitle('t3')->setLeftValue(4)->setRightValue(5)->save();
$this->assertFalse($t0->hasPrevSibling(), 'empty node has no previous sibling');
$this->assertFalse($t1->hasPrevSibling(), 'root node has no previous sibling');
$this->assertFalse($t2->hasPrevSibling(), 'first sibling has no previous sibling');
$this->assertTrue($t3->hasPrevSibling(), 'not first sibling has a previous siblingt');
}
