public function testAddScopeAndSearch()
 {
     $authorId = 1;
     $postRepo = new PostRepository();
     $posts = $postRepo->scope(function ($query) use($authorId) {
         $query->where('author_id', '=', $authorId);
     })->all();
     $this->assertTrue(count($posts) == $this->postByAuthor);
     $this->assertTrue($posts[0]->author_id == $authorId);
 }