The node's runtime is its modules' bus: it binds each module's consumer and hands its events to the bundle (hq ADR 0198)

A launched bundle's mesh/subscribe binds the module's own durable consumer — EVENTS, <node>_<module>,
by name as the module's own runtime bound it, so nothing is lost or replayed in the move — and every
event goes to each child of the module that subscribed as mesh/event, acknowledged only when all
answered, negatively acknowledged after a short delay when one failed or died, terminated when it is
not an event. mesh/ask calls a tool as the module. Every launched bundle is started again when it
exits, with backoff, since long-running code waits for no call. Requires SDK 0.1.6.

node-tools/internal/meshtest/meshtest.go

@@ -145,3 +145,40 @@ func (l *Logs) Has(fragments ...string) bool {
 
 // All is every line.
 func (l *Logs) All() string { return strings.Join(l.lines, "\n") }
+
+// Consumer makes a module's durable consumer on a machine as the controller does: pull, on the
+// EVENTS stream, filtered to what the module consumes, with a short ack wait so a test sees a
+// redelivery in seconds rather than the mesh's minutes.
+func (m *Mesh) Consumer(t *testing.T, node, module string, filters []string, ackWait time.Duration) {
+	t.Helper()
+	cfg := &nats.ConsumerConfig{Durable: node + "_" + module, AckPolicy: nats.AckExplicitPolicy,
+		AckWait: ackWait, MaxDeliver: 10, DeliverPolicy: nats.DeliverNewPolicy}
+	if len(filters) == 1 {
+		cfg.FilterSubject = filters[0]
+	} else {
+		cfg.FilterSubjects = filters
+	}
+	if _, err := m.js.AddConsumer("EVENTS", cfg); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// Emit publishes an event as a module would, into the EVENTS stream.
+func (m *Mesh) Emit(t *testing.T, subject string, body any) {
+	t.Helper()
+	data, _ := json.Marshal(body)
+	if _, err := m.js.Publish(subject, data); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// Pending is what a module's consumer still holds: delivered and not acknowledged, and not yet
+// delivered.
+func (m *Mesh) Pending(t *testing.T, node, module string) (ackPending, notDelivered uint64) {
+	t.Helper()
+	info, err := m.js.ConsumerInfo("EVENTS", node+"_"+module)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return uint64(info.NumAckPending), info.NumPending
+}