Traté de crear una prueba unitaria para las relaciones entre miUser yShop modelos, sin embargo cuando corrovendor\\bin\\phpunit se arrojan estos errores, no tengo idea de esto ya que soy un novato en pruebas unitarias. Traté de ejecutar mi código en mi controlador para ver si la relación realmente funciona, y afortunadamente funciona como se esperaba, pero no cuando se ejecuta en phpunit. ¿Qué he hecho mal para que este phpunit no funcione con modelos?

Fatal error: Uncaught Error: Call to a member function connection() on null in E:\projects\try\vendor\laravel\framework\src\Illuminate\Database\Eloquent\Model.php:1013

Stack trace: E:\projects\try\vendor\laravel\framework\src\Illuminate\Database\Eloquent\Model.php(979): Illuminate\Database\Eloquent\Model::resolveConnection(NULL)

Este es mi UserTest.php

<?php

namespace Tests\Unit;

use Tests\TestCase;
use Illuminate\Foundation\Testing\DatabaseMigrations;
use Illuminate\Foundation\Testing\DatabaseTransactions;

use App\User;
use App\Shop;

class UserTest extends TestCase
{

    protected $user, $shop;

    function __construct()
    {
        $this->setUp();
    }

    function setUp()
    {
        $user = new User([
            'id' => 1,
            'first_name' => 'John',
            'last_name' => 'Doe',
            'email' => '[email protected]',
            'password' => 'secret',
            'facebook_id' => null,
            'type' => 'customer',
            'confirmation_code' => null,
            'newsletter_subscription' => 0,
            'last_online' => null,
            'telephone' => null,
            'mobile' => null,
            'social_security_id' => null,
            'address_1' => null,
            'address_2' => null,
            'city' => null,
            'zip_code' => null,
            'signed_agreement' => 0,
            'is_email_confirmed' => 0
        ]);

        $user = User::find(1);
        $shop = new Shop([
            'id' => 1,
            'user_id' => $user->id,
            'name' => 'PureFoods Hotdog2',
            'description' => 'Something that describes this shop',
            'url' => null,
            'currency' => 'USD'
        ]);
        $user->shops()->save($shop);

        $shop = new Shop([
            'id' => 2,
            'user_id' => $user->id,
            'name' => 'PureFoods Hotdog',
            'description' => 'Something that describes this shop',
            'url' => null,
            'currency' => 'USD'
        ]);

        $user->shops()->save($shop);

        $this->user = $user;

    }

    /** @test */
    public function a_user_has_an_id(){
        $user =  User::find(1);
        $this->assertEquals(1, $user->id);
    }

    /** @test */
    public function a_user_has_a_first_name(){
        $this->assertEquals("John", $this->user->first_name);
    }

    /** @test */
    public function a_user_can_own_multiple_shops(){
        $shops = User::find(1)->shops()->get();
        var_dump($this->shops);
        $this->assertCount(2, $shops);
    }
}

Parece que este error es causado por esta línea de código:$user->shops()->save($shop); - este código realmente funciona cuando se ejecuta en mis rutas de muestra o Controlador pero está arrojandoerrors cuando se ejecuta enphpunit

User.php

<?php

namespace App;

use Illuminate\Notifications\Notifiable;
use Illuminate\Foundation\Auth\User as Authenticatable;

class User extends Authenticatable
{
    use Notifiable;

    protected $guarded = [ 'id' ];
    protected $table = "users";   

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];


    /**
     * returns the Shops that this user owned
     */
    public function shops(){
        return $this->hasMany('App\Shop');
    }
}

Shop.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Shop extends Model
{
    protected $guarded = [ 'id' ];
    protected $table = "shops";

    /**
     * returns the Owner of this Shop
     */
    public function owner(){
        return $this->belongsTo('App\User');
    }
}

Cualquier ayuda será muy apreciada. ¡Gracias!