Favorite a reply results in failed test

Following Jeffrey's Build a Forum tutorials results in failed test

PHPUnit 8.0.5 by Sebastian Bergmann and contributors.

.F                                                                  2 / 2 (100%)

Time: 347 ms, Memory: 28.00 MB

There was 1 failure:

1) Tests\Feature\FavoritesTest::an_authenticated_user_can_favorite_any_reply
Failed asserting that actual size 0 matches expected size 1.

The test is as follows

    /** @test */

    public function an_authenticated_user_can_favorite_any_reply()
    {
        $this->signIn();

        $reply = create('App\Reply');

        $this->post('replies/' . $reply->id . '/favorites');

        $this->assertCount(1, $reply->favorites);
    }

web.php is as follows

Route::post('replies/{reply}/favorites', 'FavoritesController@store');

And in the controller is the store method as below

FavoritesController.php

   public function store(Reply $reply)
   {

        Favorite::create([
            'user_id' => auth()->user()->id,
            'favorited_id' => $reply->id,
            'favorited' => get_class($reply)
          ]);       

   }

When I dd the Favorite::all() in the test after the post I get a blank array. What could I possibly be doing wrong ?