feat: add durable outbox dispatcher

server/store/outbox_test.go

@@ -1,6 +1,9 @@
 package store
 
 import (
+	"context"
+	"errors"
+	"reflect"
 	"testing"
 	"time"
 )
@@ -18,6 +21,38 @@ func TestOutboxSQLPreservesReplayableOrderedReadAndPublishAck(t *testing.T) {
 	}
 }
 
+func TestOutboxDispatcherAcknowledgesOnlyAfterDelivery(t *testing.T) {
+	events := []OutboxEvent{{EventID: "event-1"}, {EventID: "event-2"}}
+	var delivered, acknowledged []string
+	dispatcher := &OutboxDispatcher{
+		Read: func(context.Context, int) ([]OutboxEvent, error) { return events, nil },
+		Deliver: func(_ context.Context, event OutboxEvent) error {
+			delivered = append(delivered, event.EventID)
+			if event.EventID == "event-2" {
+				return errors.New("transient fan-out failure")
+			}
+			return nil
+		},
+		Ack: func(_ context.Context, eventID string, _ time.Time) error {
+			acknowledged = append(acknowledged, eventID)
+			return nil
+		},
+	}
+	count, err := dispatcher.Dispatch(context.Background(), 10, time.Unix(1000, 0))
+	if err == nil || count != 1 {
+		t.Fatalf("dispatch = (%d, %v), want one acknowledged event and an error", count, err)
+	}
+	if !reflect.DeepEqual(delivered, []string{"event-1", "event-2"}) || !reflect.DeepEqual(acknowledged, []string{"event-1"}) {
+		t.Fatalf("delivery/ack order = %v/%v", delivered, acknowledged)
+	}
+}
+
+func TestOutboxDispatcherRejectsInvalidConfiguration(t *testing.T) {
+	if count, err := (*OutboxDispatcher)(nil).Dispatch(context.Background(), 1, time.Unix(1000, 0)); err == nil || count != 0 {
+		t.Fatal("nil dispatcher accepted")
+	}
+}
+
 func TestOutboxAdaptersRejectUnsafeArgumentsWithoutDatabase(t *testing.T) {
 	if _, err := ReadUnpublishedOutbox(nil, nil, 1); err == nil {
 		t.Fatal("nil database accepted")