Laravel Unit Testing Inconsistency

Hi I am following the laravel course from laracast, but faced some difficulty following the course.

In the app, there is a Post Model with a static function that returns grouped records:

Post.php

public static function archives()
{

    return static::selectRaw('year(created_at) as year, monthname(created_at) month, count(*) published')
    ->groupBy('year', 'month')
    ->orderByRaw('min(created_at) desc')
    ->get()
    ->toArray();
}

On the other hand, a test case aims to test the Post::archives() function:

ExampleTest.php

public function testBasicTest()
{

    // GIVEN I have two records in the database that are posts,
    // and each one is posted a month apart.
    $first = factory(Post::class)->create();

    $second = factory(Post::class)->create([
       'created_at' => \Carbon\Carbon::now()->subMonth()
    ]);
    // WHEN I fetch the archives
    $posts = \App\Post::archives();
    // dd($posts);
    // THEN the response should be in the proper format
    $this->assertEquals([
        [
            "year" => $first->created_at->format('Y'),
            "month" => $first->created_at->format('F'),
            "published" => 1
        ],
        [
            "year" => $first->created_at->format('Y'),
            "month" => $first->created_at->format('F'),
            "published" => 1
        ],
    ], $posts);
}

However, the assertion failed, because $posts is an array of object instead of an array of array, even though Post::archives() specifically converted the results with toArray().

Dumping it on tinker:

$posts = \App\Post::archives()
[
 [
   "year" => 2014,
   "month" => "March",
   "published" => 2,
 ],
 [
   "year" => 2014,
   "month" => "February",
   "published" => 1,
 ],
 [
   "year" => 2013,
   "month" => "February",
   "published" => 1,
 ],
]

clearly shows it as the proper format. Why is it behaving as such in the TestCase?

via Chebli Mohamed