public async Task TestUpdateUser()
        {
            IDatabaseService provider = UserDatabaseTests.CreateProvider();
            using (CancellationTokenSource cancellationTokenSource = new CancellationTokenSource(TestTimeout(TimeSpan.FromSeconds(600))))
            {
                string host = null;
                UserName userName = UserDatabaseTests.CreateRandomUserName(host);
                string password = UserDatabaseTests.CreateRandomPassword();
                UserConfiguration userConfiguration = new UserConfiguration(userName, password);
                await provider.CreateUserAsync(_instance.Id, userConfiguration, cancellationTokenSource.Token);

                UpdateUserConfiguration updateUserConfiguration = new UpdateUserConfiguration(null, UserDatabaseTests.CreateRandomPassword());
                await provider.UpdateUserAsync(_instance.Id, userName, updateUserConfiguration, cancellationTokenSource.Token);

                await provider.RemoveUserAsync(_instance.Id, userName, cancellationTokenSource.Token);
            }
        }
        /// <summary>
        /// Update properties of a database user.
        /// </summary>
        /// <param name="service">The database service instance.</param>
        /// <param name="instanceId">The database instance ID. This is obtained from <see cref="DatabaseInstance.Id">DatabaseInstance.Id</see>.</param>
        /// <param name="userName">A <see cref="UserName"/> object identifying the database user. This is obtained from <see cref="UserConfiguration.UserName">UserConfiguration.UserName</see>.</param>
        /// <param name="configuration">An <see cref="UpdateUserConfiguration"/> object describing the updates to apply to the user.</param>
        /// <exception cref="ArgumentNullException">If <paramref name="service"/> is <see langword="null"/>.</exception>
        /// <exception cref="ArgumentNullException">
        /// If <paramref name="instanceId"/> is <see langword="null"/>.
        /// <para>-or-</para>
        /// <para>If <paramref name="userName"/> is <see langword="null"/>.</para>
        /// <para>-or-</para>
        /// <para>If <paramref name="configuration"/> is <see langword="null"/>.</para>
        /// </exception>
        /// <exception cref="WebException">If the REST request does not return successfully.</exception>
        /// <seealso href="http://docs.rackspace.com/cdb/api/v1.0/cdb-devguide/content/PUT_modifyUser__version___accountId__instances__instanceId__users__name__.html">Modify User Attributes (Rackspace Cloud Databases Developer Guide - API v1.0)</seealso>
        public static void UpdateUser(this IDatabaseService service, DatabaseInstanceId instanceId, UserName userName, UpdateUserConfiguration configuration)
        {
            if (service == null)
                throw new ArgumentNullException("service");

            try
            {
                service.UpdateUserAsync(instanceId, userName, configuration, CancellationToken.None).Wait();
            }
            catch (AggregateException ex)
            {
                ReadOnlyCollection<Exception> innerExceptions = ex.Flatten().InnerExceptions;
                if (innerExceptions.Count == 1)
                    throw innerExceptions[0];

                throw;
            }
        }