public function testInsertMultiple_Acknowledged()
{
$this->collection->setWriteConcern(1);
$this->collection->insertMultiple(array(array('a' => 1, 'b' => 2), array('a' => 3, 'b' => 4)));
$document = $this->collection->find()->where('a', 1)->findOne();
$this->assertNotEmpty($document);
$this->assertEquals(2, $document->b);
}