public void WhenAddingAlreadyParticipatingUserToChat_AddParticipantToChat_ShouldThrowException() { ChatsRepository chatsRepository = new ChatsRepository(); Guid id = Guid.NewGuid(); Channel channel = new Channel(id, "title"); var chatId = channel.GetId(); Account user = new Account("user", "password"); chatsRepository.AddUserToChat(chatId, user.Id); chatsRepository.AddUserToChat(chatId, user.Id); }