ZF2 Mock crashes on undefined method

I'm following this tutorial for unit testing on ZF2. I'm familiar with unit testing, so I pretty much understand what's going on.

I'm getting a PHP Fatal error: Call to undefined method Mock_AlbumTable_9fb22412::fetchAll() in [my controller's route here].

If I'm following correctly, the controller calls fetchAll on my mock object. The weird part is why is it undefined, if I declared it in the mock expectations.

My test code is exactly the same on the link provided, (Literally copy/pasted), and my AlbumTable class is also from the tutorial:

<?php

namespace Album\Model;

use Zend\Db\TableGateway\TableGateway;

class AlbumTable
{
    protected $tableGateway;

    public function __construct(TableGateway $tableGateway)
    {
        $this->tableGateway = $tableGateway;
    }

    public function fetchAll()
    {
        $resultSet = $this->tableGateway->select();
        return $resultSet;
    }

    // ... more code ...
}

What am I missing here?