ProtoTest.Messaging.MassTransit 1.1.3

ProtoTest.Messaging.MassTransit

Preview: the surface can change before 1.2.

Bridges the ProtoTest messaging surface to the application's MassTransit test harness: publish a command and await the events the application publishes, over the in-process ITestHarness the application composes with AddMassTransitTestHarness. The package also carries the MassTransit wire envelope (MassTransitEnvelope), so the same surface can test a published application through a real broker without a harness.

dotnet add package ProtoTest.Messaging.MassTransit

// The application under test (in-process):
builder.Services.AddMassTransitTestHarness(cfg => cfg.AddConsumer<PaymentReceivedConsumer>());

// The suite: the application's server first, then the messaging bridge.
builder.AddAspNetCoreServer<Program>();
builder.AddMessaging(messaging => messaging
    .Tap("InvoicePaid")            // snapshot the harness during setup, before the act publishes
    .UseMassTransit<Program>());

[ProtoTest]
public async Task PayingAnInvoicePublishesTheEvent()
{
    await Proto.Context.Messaging().PublishAsync("PaymentReceived", """{"invoiceId":42,"amount":10.5}""");

    var paid = await Proto.Context.Messaging().AwaitAsync(
        "InvoicePaid",
        message => message.Payload!.Contains("\"invoiceId\":42"));

    paid.Should.MatchShape(new { invoiceId = 42, amount = 10.5 });
}

A destination names a message contract type (its full name, its short name, or its urn:message: URN), because that is what a MassTransit bus addresses; the payload is JSON for that contract. The Broker capability is declared only while the application's BaseUrl is not configured, so a published application drops it and gated tests skip.

Published applications: the wire envelope

When the application runs as a real process with a real transport, register the RabbitMQ adapter and speak the wire format with MassTransitEnvelope: the frame is MassTransit's own JSON envelope (application/vnd.masstransit+json, the contract's urn:message: URNs, ids, sent time, headers), and the destination is the exchange MassTransit names after the contract (Namespace:Type):

builder.AddMessaging(messaging => messaging
    .Tap("Billing:InvoicePaid")
    .UseRabbitMq());

var frame = MassTransitEnvelope.Wrap("Billing:PaymentReceived", new PaymentReceived(42, 10.5m));
await Proto.Context.Messaging().PublishAsync(
    frame.Destination, frame.Payload, frame.Headers, frame.ContentType);

var published = await Proto.Context.Messaging().AwaitAsync("Billing:InvoicePaid", _ => true);
var paid = MassTransitEnvelope.Unwrap<InvoicePaid>(published);
var envelope = MassTransitEnvelope.Unwrap(published);   // URNs, ids, sent time, raw payload

Wrap takes the contract instance or a raw JSON payload plus its type; Unwrap/Unwrap<T> fail naming the destination when the frame is not a MassTransit envelope. Both conversions are pure and work with any broker adapter. Pass MassTransitEnvelopeAddresses when a consumer replies through RespondAsync and the test awaits the reply on the response address.

Includes

• UseMassTransit<TProgram>(application) registration on the AddMessaging chain; the adapter publishes over the harness bus and awaits the harness's published messages.
• The full messaging test surface: PublishAsync/AwaitAsync, ProtoMessage.ReadRequired<T>(), message.Should.MatchShape(shape), payload attachments, and the messaging.* trace vocabulary.
• Tap snapshots the harness during setup, so a message the act published is never missed.
• MassTransitEnvelope.Wrap/Unwrap speak the MassTransit wire envelope through any broker adapter, so a published application publishes what a MassTransit consumer expects and reads what the bus published, typed or as envelope metadata.

Limits

• The harness bridge is in-process only: UseMassTransit resolves ITestHarness from the application's AddAspNetCoreServer server, so the application must compose AddMassTransitTestHarness and the suite must register AddMessaging after the server. A published application (configured BaseUrl) has no harness here and its capability is dropped. Test a published application through the broker with MassTransitEnvelope instead.
• The harness is MassTransit's in-memory test transport, which replaces the application's real transport in the test process. The bridge tests the application's bus behaviour, not a broker.
• AwaitAsync observes what the bus published; the application's consumption is not part of the surface. Routing keys and queue destinations do not apply: a destination is a message contract type.
• Declare is a no-op: MassTransit owns message topology.
• Publishing needs a concrete message contract; an interface contract can be awaited when the application publishes it, but not published from the test.
• There is no container package for the bus: a harness-mode suite needs no container. An envelope-mode suite over RabbitMQ starts ProtoTest.Messaging.RabbitMq.Testcontainers.

Learn more

• MassTransit bridge
• Messaging integration
• API publishes an event