test: add test case for loadCount()

relates to #45

tests/HasMetaTest.php

@@ -1286,3 +1286,14 @@
     expect($post->user)->toBeInstanceOf(User::class);
     expect($post->relationLoaded('meta'))->toBeFalse();
 });
+
+it('works when using loadCount', function () {
+    $user = User::factory()->create();
+    Post::factory()->for($user)->count(3)->create();
+
+    expect($user->posts_count)->toBeNull();
+
+    $user->loadCount('posts');
+
+    expect($user->posts_count)->toBe(3);
+});

tests/Mocks/User.php

@@ -10,4 +10,9 @@ class User extends Model
     use HasFactory;
 
     protected $table = 'users';
+
+    public function posts()
+    {
+        return $this->hasMany(Post::class);
+    }
 }