Laravel Storage mock test helper

TestCase.php

<?php

use Illuminate\Support\Facades\Config;

class TestCase extends Laravel\Lumen\Testing\TestCase
{
    /**
     * Create a mock of a Storage disk. 
     * 
     * Usage:
     *     ```
     *     $storage = $this->mockStorageDisk('my-disk');
     *     $storage->shouldReceive('get')->once()->andReturn('test');
     *
     *     // test 
     *     Storage::disk('my-disk')->get('file.txt');
     *     ```
     * 
     * @param  String $disk Optional
     * @return Filesystem
     */
    protected function mockStorageDisk($disk = 'mock')
    {
        Storage::extend('mock', function () {
            return \Mockery::mock(\Illuminate\Contracts\Filesystem\Filesystem::class);
        });

        Config::set('filesystems.disks.' . $disk, ['driver' => 'mock']);
        Config::set('filesystems.default', $disk);

        return Storage::disk($disk);
    }
}

Largely taken from this post: http://laravel.io/forum/05-04-2015-how-to-mock-the-get-method-for-storage by @kofan.