public async Task CheckIfThereAreNewMessageAsync()
        {
            ApplicationDbContext db = GetDb();

            var chatGroupRepository      = new EfDeletableEntityRepository <ChatGroup>(db);
            var repository               = new EfDeletableEntityRepository <ChatMessage>(db);
            var userChatGroupsRepository = new EfDeletableEntityRepository <UserChatGroup>(db);

            var service = new ChatsService(
                repository,
                chatGroupRepository,
                userChatGroupsRepository);

            await service.CreateUsersGroupAsync(this.sender, this.receiver, "chat name");

            var groupId = await service.GetGroupIdAsync("chat name");

            var firstChatMessage = new ChatMessage()
            {
                Id          = Guid.NewGuid().ToString(),
                Receiver    = this.receiver,
                Sender      = this.sender,
                ChatGroupId = groupId,
            };

            await repository.AddAsync(firstChatMessage);

            await repository.SaveChangesAsync();

            var isMessage = await service.IsNewMessageAsync();

            Assert.True(isMessage);
        }