Transport conformance

Relayer.Testing provides TransportConformanceSuite<TIncoming, TBinding> for transport authors. It has no test-framework dependency. Each case creates a fresh fixture, runs the generated handler through the core receive pipeline, and calls the adapter's real send and settlement operations. Contract failures throw; missing endpoint capabilities return an explicit skip reason.

Add Relayer.Testing to your test project and implement ITransportConformanceFixture<TIncoming> using your native adapter. Use its existing IMessageBinding<TIncoming> as TBinding. The fixture receives the suite's isolated MessageTracing owner: pass it to the adapter's production tracing integration and enable the native client's instrumentation. The suite captures only that owner's Relayer source, so parallel fixtures do not share results.

var suite = new TransportConformanceSuite<NativeDelivery, NativeBinding>(
    async (tracing, cancellationToken) =>
        await BrokerFixture.CreateAsync(tracing, cancellationToken),
    timeout: TimeSpan.FromMinutes(2));

foreach (var scenario in Enum.GetValues<TransportConformanceCase>())
{
    var result = await suite.RunAsync(scenario, cancellationToken);
    if (result.Skipped)
        Console.WriteLine($"Skipped {scenario}: {result.SkipReason}");
}

NativeDelivery, NativeBinding and BrokerFixture above are your adapter's types. Prefer a separate parameterized test for each enum value. Translate result.Skipped into your framework's skip mechanism, preserving SkipReason; let exceptions fail the test. A broker connection failure or missing tracing is a failure, never a capability skip.

Fixture responsibilities

• Provision an empty, isolated endpoint with capacity for at least 32 small messages. Supply its destination, CloudEvents HeaderNames, expected OpenTelemetry messaging.system and native completion operation name.
• Expose the production ITransport. RegisterConsumer connects the supplied receive callback to the native consumer without adding another process span. The suite composes generated dispatch, process tracing and settlement around the callback.
• Implement SettleAsync with the production native complete, redeliver and dead-letter operations. Use their existing settlement instrumentation; do not manufacture spans to satisfy the suite. Do not settle again when the callback returns Disposition.SettledByHandler.
• Read dead letters from the actual native destination and return an owned ConformanceDeadLetter snapshot. Preserve original headers and error reason/description.
• Make DisconnectAsync interrupt the broker connection and ReconnectAsync restore connectivity, allowing the adapter to recover. For a real broker, merely stopping and restarting a healthy consumer is insufficient. The in-memory fixture uses its native stop/start lifecycle because it has no connection.
• Observe cancellation in provisioning, receive waits, fault injection and lifecycle operations. Dispose receivers and all resources owned by this fixture, including after failures. The default scenario deadline is 30 seconds; increase it explicitly for container startup.

The reference fixture and executable tests live in tests/Relayer.Conformance.Tests. Queue and partitioned log modes both run every case. Separate tests verify capability skips and prove that missing send tracing or overwritten creation headers fail.

Contracts

Case	Checks	Native capability required
SendReceiveSettle	Body/header ownership, delivery, completion and no replay after consumer restart	None
Retry	Redelivery, unchanged body/creation headers and increasing delivery count when the broker supplies one	MaxRedeliveryDelay is not null
DeadLetter	Original body/creation headers, reason/description and healthy-message progress	DeadLetter
Delay	Scheduled message arrives at or after its due time	Positive MaxDeliveryDelay
RedeliveryDelay	Redelivery arrives at or after its due time	Positive MaxRedeliveryDelay
OrderingByKey	32 messages sent with one key arrive in native send order	OrderedByKey
TracePropagation	Producer creation context survives native instrumentation; process links, operation names/kinds, native settlement and system identifier match the conventions	None
CreationContextCopies	Stored traceparent/tracestate survive repeated serialized sends; each client send links to the original creation context	None
Reconnect	Delivery resumes after connection interruption and recovery	None

Delay assertions use the smaller of 200 ms and the endpoint's native maximum. They compare the declared due time with handler entry; they do not rely on sleeps or require a maximum delivery latency. Queue settlement spans must run inside their process span. Log commits may be amortized outside processing, as the native log model requires.

The copy contract exercises the adapter boundary used by outbox dispatch, scheduled re-sends and dead-letter copies. It does not run a durable outbox worker or replace its integration tests. Native dead-letter preservation has its own case. Transport-specific restart/rebalance chaos tests, batching, replay, transactions and client-specific guarantees remain additional adapter tests.