Testing

Full Stack Without Redis

The plugin runs completely on the in-memory driver — CAS Lua scripts included:

import { Test } from '@nestjs/testing';
import { RedisModule } from '@nestjs-redisx/core';
import { MEMORY_DRIVER_TYPE } from '@nestjs-redisx/testing';
import { LeaderPlugin, LEADER_SERVICE, type ILeaderService } from '@nestjs-redisx/leader';

const app = await Test.createTestingModule({
  imports: [
    RedisModule.forRoot({
      clients: { type: 'single', host: 'unused', port: 1 },
      global: { driver: MEMORY_DRIVER_TYPE },
      plugins: [new LeaderPlugin({ ttlMs: 500, renewIntervalMs: 100, retryIntervalMs: 100 })],
    }),
  ],
}).compile();
await app.init();

const leader = app.get<ILeaderService>(LEADER_SERVICE);
expect(leader.isLeader()).toBe(true); // the single instance leads right after init

The first election round is awaited during onModuleInit, so leadership is deterministic by the time app.init() resolves — no sleeps needed for the single-instance case.

Simulating a Second Instance

Two competing "instances" are two LeaderService objects over the same store:

import { LeaderService, LEADER_STORE, type ILeaderStore } from '@nestjs-redisx/leader';

const nodeB = new LeaderService(
  { ttlMs: 500, renewIntervalMs: 100, retryIntervalMs: 100, instanceId: 'node-b' },
  app.get<ILeaderStore>(LEADER_STORE),
);
await nodeB.onModuleInit();

expect(nodeB.isLeader()).toBe(false); // the app instance already leads

await app.get<ILeaderService>(LEADER_SERVICE).stepDown();
await new Promise((r) => setTimeout(r, 300));
expect(nodeB.isLeader()).toBe(true); // failover

await nodeB.onModuleDestroy(); // always stop manual instances

Unit Testing Leader-Gated Services

For plain unit tests, don't run elections at all — the decorator resolves the service through a lazy getter you can point at a stub:

import { registerLeaderServiceGetter } from '@nestjs-redisx/leader';

beforeEach(() => {
  registerLeaderServiceGetter(() => ({ isLeader: () => true })); // this test IS the leader
});

afterEach(() => {
  registerLeaderServiceGetter(null); // back to fail-safe skip
});

With no getter registered, @LeaderOnly methods skip (resolve to undefined) — which is also worth asserting for the follower path.

Timing Guidance

• Use small ttlMs/renewIntervalMs/retryIntervalMs (hundreds of ms) and real waits in integration tests; the loop reads Date.now().
• Keep renewIntervalMs < ttlMs even in tests — validation is fail-fast.

Next Steps

• Testing utilities — the in-memory driver reference
• Recipes — patterns worth covering with tests