public function test_has_all()
 {
     $this->assertTrue($this->store->set('foo', 'bar'));
     $this->assertTrue($this->store->set('bat', 'baz'));
     $this->assertTrue($this->store->has_all(array('foo', 'bat')));
     $this->assertFalse($this->store->has_all(array('foo', 'bat', 'this')));
 }