public function test_join()
 {
     $qb = new QueryBuilder();
     $qb->addTable('first');
     $qb->addTable('second');
     $qb->addTable('third');
     $qb->addLeftJoin('second', 'fourth', 'fourth', 'second.foo=fourth.foo');
     $this->assertEquals(array('first', 'second', 'fourth', 'third'), array_keys($qb->from));
 }