The goal of this project is to develop an in-memory emulator for Google Cloud Pub/Sub, enabling this module to be used as a drop-in replacement for @google-cloud/pubsub in integration tests.

As an alternative to this package, you may consider using a Pub/Sub emulator Docker image. However, this package is recommended if the Docker-based emulator does not meet your performance requirements.

npm install mock-google-cloud-pubsub -D

This package implements a subset of the official Pub/Sub API. While simple use cases—such as the example shown below—are supported, you should verify compatibility with more complex scenarios as needed.

import { PubSub } from 'mock-google-cloud-pubsub';
const pubsub = new PubSub();

const [topic] = await pubsub.createTopic(topicName);
const [subscription] = await topic.createSubscription(subscriptionName);

subscription.on('message', (message) => {
  console.log('Received message:', message.data.toString());
});

topic.publish(Buffer.from('Test message!'));

Pull request for covering more features are welcome, just make sure to write tests for them.

Instead of using the actual @google-cloud/pubsub package, replace it with mock-google-cloud-pubsub during integration testing:

import { PubSub } from '@google-cloud/pubsub'
import { PubSub: MockPubSub } from 'mock-google-cloud-pubsub'

const pubsub = process.env.NODE_ENV !== 'test' ? new PubSub({ ... }) : new MockPubSub()

const [topics] = await pubsub();

const [subscriptions] = await topic.getSubscriptions();

const [subscriptions] = await pubsub.getSubscriptions();

Tests cases are run both for an actual and the mocked version, to ensure they work the same way.

To setup connection for real pubsub

• create a confidential.env file in root
• set GCP_PROJECT_ID=<your-project-id>
• set GCP_CREDENTIALS=<credentials for a service account as json>

You can use the docker pubsub emulator instead of the real pubsub:

• run docker-compose up -d
• in confidential.env set GCP_PROJECT_ID=mock-gcp-project and PUBSUB_EMULATOR_HOST=localhost:8685

Run tests with npm t or npm run test:watch for watch mode.