Testing with FakeClock

Retries and delays are scheduled in the future. FakeClock from @relaybus/testing lets a test advance time instead of sleeping.

pnpm add -D @relaybus/testing vitest

NestJS

Use the in-memory store and turn the dispatcher off so the test controls when deliveries run:

import { Test } from '@nestjs/testing';
import { InMemoryEventStore, RelayBus } from '@relaybus/core';
import { RelayBusModule } from '@relaybus/nestjs';
import { FakeClock } from '@relaybus/testing';

const clock = new FakeClock('2026-01-01T00:00:00Z');
const moduleRef = await Test.createTestingModule({
  imports: [
    RelayBusModule.forRoot({
      store: new InMemoryEventStore(),
      dispatcher: { enabled: false },
      clock,
    }),
    AppFeatureModule,
  ],
}).compile();
await moduleRef.init();

await moduleRef.get(OrderService).place('o-1');
await moduleRef.get(RelayBus).drain(); // runs every due delivery

clock.advance(5_000); // make retries due
await moduleRef.get(RelayBus).drain();

• bus.runOnce() runs a single batch; bus.drain() loops until nothing is due.
• bus.listDeliveries({ status: 'dead' }) shows handlers that exhausted their retries.
• esbuild does not emit decorator metadata, so use explicit @Inject(Token) in test classes under Vitest.

Testing your own store

Run eventStoreContract from @relaybus/testing against a real database to prove a custom EventStore behaves like the built-in ones. See @relaybus/testing.