diff --git a/src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs b/src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs
index 5a2b969..f4abede 100644
--- a/src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs
+++ b/src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs
@@ -5,6 +5,7 @@ using ScadaLink.Commons.Entities.Notifications;
 using ScadaLink.Commons.Interfaces.Repositories;
 using ScadaLink.Commons.Messages.Notification;
 using ScadaLink.Commons.Types.Enums;
+using ScadaLink.Commons.Types.Notifications;
 using ScadaLink.NotificationOutbox.Delivery;
 using ScadaLink.NotificationOutbox.Messages;
 
@@ -55,6 +56,11 @@ public class NotificationOutboxActor : ReceiveActor, IWithTimers
         Receive<InternalMessages.IngestPersisted>(HandleIngestPersisted);
         Receive<InternalMessages.DispatchTick>(_ => HandleDispatchTick());
         Receive<InternalMessages.DispatchComplete>(_ => _dispatching = false);
+        Receive<NotificationOutboxQueryRequest>(HandleQuery);
+        Receive<NotificationStatusQuery>(HandleStatusQuery);
+        Receive<RetryNotificationRequest>(HandleRetry);
+        Receive<DiscardNotificationRequest>(HandleDiscard);
+        Receive<NotificationKpiRequest>(HandleKpiRequest);
     }
 
     /// <summary>
@@ -281,6 +287,242 @@ public class NotificationOutboxActor : ReceiveActor, IWithTimers
         await outboxRepository.UpdateAsync(notification);
     }
 
+    /// <summary>
+    /// Handles a paginated, filtered query over the outbox. Builds a
+    /// <see cref="NotificationOutboxFilter"/> from the request (parsing the string status/type
+    /// filters to their enums and deriving the stuck cutoff when <c>StuckOnly</c> is set),
+    /// runs the query on a scoped repository, and pipes the mapped response back to the
+    /// captured sender. A repository fault yields a failure response with an empty list.
+    /// </summary>
+    private void HandleQuery(NotificationOutboxQueryRequest request)
+    {
+        var sender = Sender;
+        var now = DateTimeOffset.UtcNow;
+        var stuckThreshold = _options.StuckAgeThreshold;
+
+        QueryOutboxAsync(request, now, stuckThreshold).PipeTo(
+            sender,
+            success: response => response,
+            failure: ex => new NotificationOutboxQueryResponse(
+                request.CorrelationId,
+                Success: false,
+                ErrorMessage: ex.GetBaseException().Message,
+                Notifications: Array.Empty<NotificationSummary>(),
+                TotalCount: 0));
+    }
+
+    private async Task<NotificationOutboxQueryResponse> QueryOutboxAsync(
+        NotificationOutboxQueryRequest request, DateTimeOffset now, TimeSpan stuckThreshold)
+    {
+        var filter = new NotificationOutboxFilter(
+            Status: ParseEnum<NotificationStatus>(request.StatusFilter),
+            Type: ParseEnum<NotificationType>(request.TypeFilter),
+            SourceSiteId: request.SourceSiteFilter,
+            ListName: request.ListNameFilter,
+            SubjectKeyword: request.SubjectKeyword,
+            StuckOnly: request.StuckOnly,
+            StuckCutoff: request.StuckOnly ? now - stuckThreshold : null,
+            From: request.From,
+            To: request.To);
+
+        using var scope = _serviceProvider.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<INotificationOutboxRepository>();
+        var (rows, totalCount) = await repository.QueryAsync(filter, request.PageNumber, request.PageSize);
+
+        var stuckCutoff = now - stuckThreshold;
+        var summaries = rows
+            .Select(row => new NotificationSummary(
+                row.NotificationId,
+                row.Type.ToString(),
+                row.ListName,
+                row.Subject,
+                row.Status.ToString(),
+                row.RetryCount,
+                row.LastError,
+                row.SourceSiteId,
+                row.SourceInstanceId,
+                row.CreatedAt,
+                row.DeliveredAt,
+                IsStuck: IsStuck(row, stuckCutoff)))
+            .ToList();
+
+        return new NotificationOutboxQueryResponse(
+            request.CorrelationId, Success: true, ErrorMessage: null, summaries, totalCount);
+    }
+
+    /// <summary>
+    /// Handles a single-notification status query. Replies <c>Found: false</c> with empty
+    /// detail when no row matches, otherwise the row's current status, retry count, last
+    /// error, and delivery time.
+    /// </summary>
+    private void HandleStatusQuery(NotificationStatusQuery query)
+    {
+        var sender = Sender;
+
+        StatusQueryAsync(query).PipeTo(
+            sender,
+            success: response => response,
+            failure: _ => new NotificationStatusResponse(
+                query.CorrelationId, Found: false, Status: string.Empty,
+                RetryCount: 0, LastError: null, DeliveredAt: null));
+    }
+
+    private async Task<NotificationStatusResponse> StatusQueryAsync(NotificationStatusQuery query)
+    {
+        using var scope = _serviceProvider.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<INotificationOutboxRepository>();
+        var notification = await repository.GetByIdAsync(query.NotificationId);
+
+        if (notification is null)
+        {
+            return new NotificationStatusResponse(
+                query.CorrelationId, Found: false, Status: string.Empty,
+                RetryCount: 0, LastError: null, DeliveredAt: null);
+        }
+
+        return new NotificationStatusResponse(
+            query.CorrelationId,
+            Found: true,
+            Status: notification.Status.ToString(),
+            RetryCount: notification.RetryCount,
+            LastError: notification.LastError,
+            DeliveredAt: notification.DeliveredAt);
+    }
+
+    /// <summary>
+    /// Handles a manual retry request. Only a <c>Parked</c> notification can be retried;
+    /// it is reset to <c>Pending</c> with a cleared retry count, next-attempt time, and
+    /// last error so the dispatch loop re-claims it on the next sweep.
+    /// </summary>
+    private void HandleRetry(RetryNotificationRequest request)
+    {
+        var sender = Sender;
+
+        RetryAsync(request).PipeTo(
+            sender,
+            success: response => response,
+            failure: ex => new RetryNotificationResponse(
+                request.CorrelationId, Success: false, ErrorMessage: ex.GetBaseException().Message));
+    }
+
+    private async Task<RetryNotificationResponse> RetryAsync(RetryNotificationRequest request)
+    {
+        using var scope = _serviceProvider.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<INotificationOutboxRepository>();
+        var notification = await repository.GetByIdAsync(request.NotificationId);
+
+        if (notification is null)
+        {
+            return new RetryNotificationResponse(
+                request.CorrelationId, Success: false, ErrorMessage: "notification not found");
+        }
+
+        if (notification.Status != NotificationStatus.Parked)
+        {
+            return new RetryNotificationResponse(
+                request.CorrelationId, Success: false,
+                ErrorMessage: "only parked notifications can be retried");
+        }
+
+        notification.Status = NotificationStatus.Pending;
+        notification.RetryCount = 0;
+        notification.NextAttemptAt = null;
+        notification.LastError = null;
+        await repository.UpdateAsync(notification);
+
+        return new RetryNotificationResponse(request.CorrelationId, Success: true, ErrorMessage: null);
+    }
+
+    /// <summary>
+    /// Handles a manual discard request. Only a <c>Parked</c> notification can be discarded;
+    /// it is moved to the terminal <c>Discarded</c> status.
+    /// </summary>
+    private void HandleDiscard(DiscardNotificationRequest request)
+    {
+        var sender = Sender;
+
+        DiscardAsync(request).PipeTo(
+            sender,
+            success: response => response,
+            failure: ex => new DiscardNotificationResponse(
+                request.CorrelationId, Success: false, ErrorMessage: ex.GetBaseException().Message));
+    }
+
+    private async Task<DiscardNotificationResponse> DiscardAsync(DiscardNotificationRequest request)
+    {
+        using var scope = _serviceProvider.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<INotificationOutboxRepository>();
+        var notification = await repository.GetByIdAsync(request.NotificationId);
+
+        if (notification is null)
+        {
+            return new DiscardNotificationResponse(
+                request.CorrelationId, Success: false, ErrorMessage: "notification not found");
+        }
+
+        if (notification.Status != NotificationStatus.Parked)
+        {
+            return new DiscardNotificationResponse(
+                request.CorrelationId, Success: false,
+                ErrorMessage: "only parked notifications can be discarded");
+        }
+
+        notification.Status = NotificationStatus.Discarded;
+        await repository.UpdateAsync(notification);
+
+        return new DiscardNotificationResponse(request.CorrelationId, Success: true, ErrorMessage: null);
+    }
+
+    /// <summary>
+    /// Handles a KPI snapshot request, computing the outbox metrics with the stuck cutoff
+    /// derived from <see cref="NotificationOutboxOptions.StuckAgeThreshold"/> and the
+    /// delivered window from <see cref="NotificationOutboxOptions.DeliveredKpiWindow"/>.
+    /// </summary>
+    private void HandleKpiRequest(NotificationKpiRequest request)
+    {
+        var sender = Sender;
+        var now = DateTimeOffset.UtcNow;
+        var stuckCutoff = now - _options.StuckAgeThreshold;
+        var deliveredSince = now - _options.DeliveredKpiWindow;
+
+        ComputeKpisAsync(request.CorrelationId, stuckCutoff, deliveredSince).PipeTo(sender);
+    }
+
+    private async Task<NotificationKpiResponse> ComputeKpisAsync(
+        string correlationId, DateTimeOffset stuckCutoff, DateTimeOffset deliveredSince)
+    {
+        using var scope = _serviceProvider.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<INotificationOutboxRepository>();
+        var snapshot = await repository.ComputeKpisAsync(stuckCutoff, deliveredSince);
+
+        return new NotificationKpiResponse(
+            correlationId,
+            snapshot.QueueDepth,
+            snapshot.StuckCount,
+            snapshot.ParkedCount,
+            snapshot.DeliveredLastInterval,
+            snapshot.OldestPendingAge);
+    }
+
+    /// <summary>
+    /// A notification counts as stuck when it is still in a non-terminal status
+    /// (<c>Pending</c> or <c>Retrying</c>) and was created before the supplied cutoff.
+    /// </summary>
+    private static bool IsStuck(Notification notification, DateTimeOffset stuckCutoff)
+    {
+        return notification.Status is NotificationStatus.Pending or NotificationStatus.Retrying
+            && notification.CreatedAt < stuckCutoff;
+    }
+
+    /// <summary>
+    /// Parses a string filter value to a nullable enum, ignoring case. An empty, whitespace,
+    /// or unrecognised value yields <c>null</c> — meaning "no constraint on that dimension".
+    /// </summary>
+    private static TEnum? ParseEnum<TEnum>(string? value) where TEnum : struct, Enum
+    {
+        return Enum.TryParse<TEnum>(value, ignoreCase: true, out var parsed) ? parsed : null;
+    }
+
     private static Notification BuildNotification(NotificationSubmit msg)
     {
         // All current notifications are email; NotificationType has only the Email member.
diff --git a/tests/ScadaLink.NotificationOutbox.Tests/NotificationOutboxActorQueryTests.cs b/tests/ScadaLink.NotificationOutbox.Tests/NotificationOutboxActorQueryTests.cs
new file mode 100644
index 0000000..77616fe
--- /dev/null
+++ b/tests/ScadaLink.NotificationOutbox.Tests/NotificationOutboxActorQueryTests.cs
@@ -0,0 +1,335 @@
+using Akka.Actor;
+using Akka.TestKit.Xunit2;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging.Abstractions;
+using NSubstitute;
+using NSubstitute.ExceptionExtensions;
+using ScadaLink.Commons.Entities.Notifications;
+using ScadaLink.Commons.Interfaces.Repositories;
+using ScadaLink.Commons.Messages.Notification;
+using ScadaLink.Commons.Types.Enums;
+using ScadaLink.Commons.Types.Notifications;
+using ScadaLink.NotificationOutbox.Delivery;
+
+namespace ScadaLink.NotificationOutbox.Tests;
+
+/// <summary>
+/// Task 15: Tests for the <see cref="NotificationOutboxActor"/> query surface — the
+/// paginated outbox query, single-notification status query, manual retry and discard
+/// of parked notifications, and the KPI snapshot.
+/// </summary>
+public class NotificationOutboxActorQueryTests : TestKit
+{
+    private readonly INotificationOutboxRepository _repository =
+        Substitute.For<INotificationOutboxRepository>();
+
+    private IServiceProvider BuildServiceProvider()
+    {
+        var services = new ServiceCollection();
+        services.AddScoped(_ => _repository);
+        return services.BuildServiceProvider();
+    }
+
+    private IActorRef CreateActor(NotificationOutboxOptions? options = null)
+    {
+        return Sys.ActorOf(Props.Create(() => new NotificationOutboxActor(
+            BuildServiceProvider(),
+            // A long dispatch interval keeps the dispatch loop from interfering with these tests.
+            options ?? new NotificationOutboxOptions { DispatchInterval = TimeSpan.FromHours(1) },
+            NullLogger<NotificationOutboxActor>.Instance,
+            new Dictionary<NotificationType, INotificationDeliveryAdapter>())));
+    }
+
+    private static Notification MakeNotification(
+        NotificationStatus status = NotificationStatus.Pending,
+        DateTimeOffset? createdAt = null,
+        int retryCount = 0,
+        string? lastError = null,
+        DateTimeOffset? deliveredAt = null)
+    {
+        return new Notification(
+            Guid.NewGuid().ToString(), NotificationType.Email, "ops-team", "Subject", "Body", "site-1")
+        {
+            Status = status,
+            CreatedAt = createdAt ?? DateTimeOffset.UtcNow,
+            RetryCount = retryCount,
+            LastError = lastError,
+            DeliveredAt = deliveredAt,
+            SourceInstanceId = "instance-42",
+        };
+    }
+
+    [Fact]
+    public void Query_PassesFilterFromRequest_AndMapsRowsToSummaries()
+    {
+        var now = DateTimeOffset.UtcNow;
+        var staleRow = MakeNotification(
+            status: NotificationStatus.Pending, createdAt: now - TimeSpan.FromHours(1));
+        var freshRow = MakeNotification(
+            status: NotificationStatus.Pending, createdAt: now);
+        _repository.QueryAsync(
+                Arg.Any<NotificationOutboxFilter>(), Arg.Any<int>(), Arg.Any<int>(), Arg.Any<CancellationToken>())
+            .Returns(((IReadOnlyList<Notification>)new[] { staleRow, freshRow }, 2));
+        var actor = CreateActor();
+
+        actor.Tell(
+            new NotificationOutboxQueryRequest(
+                CorrelationId: "corr-1",
+                StatusFilter: null,
+                TypeFilter: null,
+                SourceSiteFilter: "site-1",
+                ListNameFilter: "ops-team",
+                StuckOnly: false,
+                SubjectKeyword: "tank",
+                From: null,
+                To: null,
+                PageNumber: 2,
+                PageSize: 25),
+            TestActor);
+
+        var response = ExpectMsg<NotificationOutboxQueryResponse>();
+        Assert.Equal("corr-1", response.CorrelationId);
+        Assert.True(response.Success);
+        Assert.Null(response.ErrorMessage);
+        Assert.Equal(2, response.TotalCount);
+        Assert.Equal(2, response.Notifications.Count);
+
+        _repository.Received(1).QueryAsync(
+            Arg.Is<NotificationOutboxFilter>(f =>
+                f.SourceSiteId == "site-1" &&
+                f.ListName == "ops-team" &&
+                f.SubjectKeyword == "tank" &&
+                f.Status == null &&
+                f.Type == null &&
+                f.StuckOnly == false),
+            2, 25, Arg.Any<CancellationToken>());
+
+        // IsStuck: the hour-old Pending row is stuck, the just-created one is not.
+        var staleSummary = response.Notifications.Single(s => s.NotificationId == staleRow.NotificationId);
+        var freshSummary = response.Notifications.Single(s => s.NotificationId == freshRow.NotificationId);
+        Assert.True(staleSummary.IsStuck);
+        Assert.False(freshSummary.IsStuck);
+        Assert.Equal("Pending", staleSummary.Status);
+        Assert.Equal("Email", staleSummary.Type);
+        Assert.Equal("site-1", staleSummary.SourceSiteId);
+    }
+
+    [Fact]
+    public void Query_WithStatusFilterString_ParsesToEnumOnFilter()
+    {
+        _repository.QueryAsync(
+                Arg.Any<NotificationOutboxFilter>(), Arg.Any<int>(), Arg.Any<int>(), Arg.Any<CancellationToken>())
+            .Returns(((IReadOnlyList<Notification>)Array.Empty<Notification>(), 0));
+        var actor = CreateActor();
+
+        actor.Tell(
+            new NotificationOutboxQueryRequest(
+                CorrelationId: "corr-2",
+                StatusFilter: "Parked",
+                TypeFilter: "Email",
+                SourceSiteFilter: null,
+                ListNameFilter: null,
+                StuckOnly: true,
+                SubjectKeyword: null,
+                From: null,
+                To: null,
+                PageNumber: 1,
+                PageSize: 50),
+            TestActor);
+
+        ExpectMsg<NotificationOutboxQueryResponse>();
+
+        _repository.Received(1).QueryAsync(
+            Arg.Is<NotificationOutboxFilter>(f =>
+                f.Status == NotificationStatus.Parked &&
+                f.Type == NotificationType.Email &&
+                f.StuckOnly == true &&
+                f.StuckCutoff != null),
+            1, 50, Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public void Query_RepositoryThrows_RepliesFailureWithEmptyList()
+    {
+        _repository.QueryAsync(
+                Arg.Any<NotificationOutboxFilter>(), Arg.Any<int>(), Arg.Any<int>(), Arg.Any<CancellationToken>())
+            .ThrowsAsync(new InvalidOperationException("db down"));
+        var actor = CreateActor();
+
+        actor.Tell(
+            new NotificationOutboxQueryRequest(
+                "corr-err", null, null, null, null, false, null, null, null, 1, 50),
+            TestActor);
+
+        var response = ExpectMsg<NotificationOutboxQueryResponse>();
+        Assert.Equal("corr-err", response.CorrelationId);
+        Assert.False(response.Success);
+        Assert.NotNull(response.ErrorMessage);
+        Assert.Contains("db down", response.ErrorMessage);
+        Assert.Empty(response.Notifications);
+    }
+
+    [Fact]
+    public void StatusQuery_Found_RepliesWithRowDetail()
+    {
+        var row = MakeNotification(
+            status: NotificationStatus.Retrying, retryCount: 3, lastError: "smtp timeout");
+        _repository.GetByIdAsync(row.NotificationId, Arg.Any<CancellationToken>()).Returns(row);
+        var actor = CreateActor();
+
+        actor.Tell(new NotificationStatusQuery("corr-3", row.NotificationId), TestActor);
+
+        var response = ExpectMsg<NotificationStatusResponse>();
+        Assert.Equal("corr-3", response.CorrelationId);
+        Assert.True(response.Found);
+        Assert.Equal("Retrying", response.Status);
+        Assert.Equal(3, response.RetryCount);
+        Assert.Equal("smtp timeout", response.LastError);
+    }
+
+    [Fact]
+    public void StatusQuery_NotFound_RepliesFoundFalse()
+    {
+        _repository.GetByIdAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
+            .Returns((Notification?)null);
+        var actor = CreateActor();
+
+        actor.Tell(new NotificationStatusQuery("corr-4", "missing-id"), TestActor);
+
+        var response = ExpectMsg<NotificationStatusResponse>();
+        Assert.Equal("corr-4", response.CorrelationId);
+        Assert.False(response.Found);
+        Assert.Equal(string.Empty, response.Status);
+        Assert.Equal(0, response.RetryCount);
+    }
+
+    [Fact]
+    public void Retry_ParkedNotification_ResetsToPending_AndSucceeds()
+    {
+        var row = MakeNotification(status: NotificationStatus.Parked, retryCount: 10, lastError: "gave up");
+        row.NextAttemptAt = DateTimeOffset.UtcNow;
+        _repository.GetByIdAsync(row.NotificationId, Arg.Any<CancellationToken>()).Returns(row);
+        var actor = CreateActor();
+
+        actor.Tell(new RetryNotificationRequest("corr-5", row.NotificationId), TestActor);
+
+        var response = ExpectMsg<RetryNotificationResponse>();
+        Assert.Equal("corr-5", response.CorrelationId);
+        Assert.True(response.Success);
+        Assert.Null(response.ErrorMessage);
+
+        _repository.Received(1).UpdateAsync(
+            Arg.Is<Notification>(n =>
+                n.NotificationId == row.NotificationId &&
+                n.Status == NotificationStatus.Pending &&
+                n.RetryCount == 0 &&
+                n.NextAttemptAt == null &&
+                n.LastError == null),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public void Retry_NonParkedNotification_Fails()
+    {
+        var row = MakeNotification(status: NotificationStatus.Delivered);
+        _repository.GetByIdAsync(row.NotificationId, Arg.Any<CancellationToken>()).Returns(row);
+        var actor = CreateActor();
+
+        actor.Tell(new RetryNotificationRequest("corr-6", row.NotificationId), TestActor);
+
+        var response = ExpectMsg<RetryNotificationResponse>();
+        Assert.False(response.Success);
+        Assert.NotNull(response.ErrorMessage);
+        _repository.DidNotReceive().UpdateAsync(Arg.Any<Notification>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public void Retry_MissingNotification_Fails()
+    {
+        _repository.GetByIdAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
+            .Returns((Notification?)null);
+        var actor = CreateActor();
+
+        actor.Tell(new RetryNotificationRequest("corr-7", "missing-id"), TestActor);
+
+        var response = ExpectMsg<RetryNotificationResponse>();
+        Assert.False(response.Success);
+        Assert.NotNull(response.ErrorMessage);
+        Assert.Contains("not found", response.ErrorMessage);
+    }
+
+    [Fact]
+    public void Discard_ParkedNotification_MarksDiscarded_AndSucceeds()
+    {
+        var row = MakeNotification(status: NotificationStatus.Parked);
+        _repository.GetByIdAsync(row.NotificationId, Arg.Any<CancellationToken>()).Returns(row);
+        var actor = CreateActor();
+
+        actor.Tell(new DiscardNotificationRequest("corr-8", row.NotificationId), TestActor);
+
+        var response = ExpectMsg<DiscardNotificationResponse>();
+        Assert.Equal("corr-8", response.CorrelationId);
+        Assert.True(response.Success);
+
+        _repository.Received(1).UpdateAsync(
+            Arg.Is<Notification>(n => n.Status == NotificationStatus.Discarded),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public void Discard_NonParkedNotification_Fails()
+    {
+        var row = MakeNotification(status: NotificationStatus.Pending);
+        _repository.GetByIdAsync(row.NotificationId, Arg.Any<CancellationToken>()).Returns(row);
+        var actor = CreateActor();
+
+        actor.Tell(new DiscardNotificationRequest("corr-9", row.NotificationId), TestActor);
+
+        var response = ExpectMsg<DiscardNotificationResponse>();
+        Assert.False(response.Success);
+        Assert.NotNull(response.ErrorMessage);
+        _repository.DidNotReceive().UpdateAsync(Arg.Any<Notification>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public void Discard_MissingNotification_Fails()
+    {
+        _repository.GetByIdAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
+            .Returns((Notification?)null);
+        var actor = CreateActor();
+
+        actor.Tell(new DiscardNotificationRequest("corr-10", "missing-id"), TestActor);
+
+        var response = ExpectMsg<DiscardNotificationResponse>();
+        Assert.False(response.Success);
+        Assert.Contains("not found", response.ErrorMessage);
+    }
+
+    [Fact]
+    public void KpiRequest_ComputesKpis_AndMapsSnapshot()
+    {
+        var snapshot = new NotificationKpiSnapshot(
+            QueueDepth: 7,
+            StuckCount: 2,
+            ParkedCount: 3,
+            DeliveredLastInterval: 12,
+            OldestPendingAge: TimeSpan.FromMinutes(4));
+        _repository.ComputeKpisAsync(
+                Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(), Arg.Any<CancellationToken>())
+            .Returns(snapshot);
+        var actor = CreateActor();
+
+        actor.Tell(new NotificationKpiRequest("corr-11"), TestActor);
+
+        var response = ExpectMsg<NotificationKpiResponse>();
+        Assert.Equal("corr-11", response.CorrelationId);
+        Assert.Equal(7, response.QueueDepth);
+        Assert.Equal(2, response.StuckCount);
+        Assert.Equal(3, response.ParkedCount);
+        Assert.Equal(12, response.DeliveredLastInterval);
+        Assert.Equal(TimeSpan.FromMinutes(4), response.OldestPendingAge);
+
+        _repository.Received(1).ComputeKpisAsync(
+            Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(), Arg.Any<CancellationToken>());
+    }
+}