private void TopicWith_PostsAnd_Attachments(int postCount, int attachmentCount)
 {
     _topic = TopicFixtures.TopicWithNoPostsAndNoAttachments(1);
     for (var i = 0; i < postCount; i++)
     {
         _topic.Add(PostFixtures.RootPostWithNoChildren(i));
     }
     for (var i = 0; i < attachmentCount; i++)
     {
         _topic.Add(AttachmentFixtures.Attachment(i));
     }
 }