public async Task <IGrainReminder> RegisterOrUpdateReminder(string reminderName, TimeSpan dueTime, TimeSpan period)
        {
            await Mock.Object.RegisterOrUpdateReminder(reminderName, dueTime, period);

            var reminder = new TestReminder(reminderName, dueTime, period);

            _reminders[reminderName] = reminder;

            return(reminder);
        }
        public async Task <IGrainReminder> RegisterOrUpdateReminder(string reminderName, TimeSpan dueTime, TimeSpan period)
        {
            if (reminderName == null)
            {
                throw new ArgumentNullException(nameof(reminderName));
            }

            await Mock.Object.RegisterOrUpdateReminder(reminderName, dueTime, period).ConfigureAwait(false);

            var reminder = new TestReminder(reminderName, dueTime, period);

            _reminders[reminderName] = reminder;
            return(reminder);
        }