Official emulators

Some services already ship an official local emulator that their SDKs know how to reach. Baseline does not reimplement those. Run the vendor’s emulator next to Baseline instead: you get the vendor’s own fidelity, and Baseline covers the services that have no local option.

Service	Official emulator	How the SDK finds it
Firebase Auth, Firestore, Storage	Firebase Local Emulator Suite	`FIREBASE_AUTH_EMULATOR_HOST`, `FIRESTORE_EMULATOR_HOST`, `FIREBASE_STORAGE_EMULATOR_HOST`
Azure Blob Storage	Azurite	Connection string `UseDevelopmentStorage=true`
Google Cloud Pub/Sub	Pub/Sub emulator in the gcloud CLI	`PUBSUB_EMULATOR_HOST`

Google Cloud Storage has no official emulator, so it is on Baseline’s own roadmap. For gRPC services in general, see WebSockets.

Firebase

The Emulator Suite needs the Firebase CLI and a Java runtime (see Firebase’s install guide for the minimum JDK version). Initialize the emulators you want once:

npx firebase-tools init emulators

Then point the Admin SDK at them. The Admin SDK reads these variables and skips real credentials when they are set:

FIREBASE_AUTH_EMULATOR_HOST=127.0.0.1:9099
FIRESTORE_EMULATOR_HOST=127.0.0.1:8080
FIREBASE_STORAGE_EMULATOR_HOST=127.0.0.1:9199
GCLOUD_PROJECT=demo-baseline

A project id starting with demo- tells the Firebase tools that no real project exists, so nothing can reach production. In the browser SDK, call connectAuthEmulator, connectFirestoreEmulator, and connectStorageEmulator instead.

Azure Blob Storage

Azurite is an npm package, so it needs nothing but Node:

npx azurite --silent --location .azurite

Blob storage listens on port 10000 (queues on 10001, tables on 10002). @azure/storage-blob connects with the well known development connection string:

import { BlobServiceClient } from "@azure/storage-blob";

const blobs = BlobServiceClient.fromConnectionString(
  process.env.AZURE_STORAGE_CONNECTION_STRING ?? "UseDevelopmentStorage=true",
);

Google Cloud Pub/Sub

The Pub/Sub emulator ships with the gcloud CLI (gcloud components install pubsub-emulator) and also needs Java:

gcloud beta emulators pubsub start --project=demo-baseline --host-port=127.0.0.1:8085

@google-cloud/pubsub connects to it when PUBSUB_EMULATOR_HOST is set:

PUBSUB_EMULATOR_HOST=127.0.0.1:8085
PUBSUB_PROJECT_ID=demo-baseline

The emulator keeps topics and subscriptions in memory only, so create them at the start of each test run.

Running them together

Start everything from one package.json script with concurrently. Baseline serves the providers in baseline.config.json, and each official emulator serves its own:

baseline.config.json

{
  "github": {},
  "google": {},
  "stripe": {}
}

{
  "scripts": {
    "emulators": "concurrently -n baseline,firebase,azurite,pubsub \"baseline start\" \"firebase emulators:start --project demo-baseline\" \"azurite --silent --location .azurite\" \"gcloud beta emulators pubsub start --project=demo-baseline --host-port=127.0.0.1:8085\""
  }
}

Keep the variables in one .env.test so your app sees Baseline’s URLs and the official emulators’ hosts together:

# Baseline providers (default ports; the variable names are whatever your app reads)
GITHUB_API_URL=http://localhost:4001
GOOGLE_API_URL=http://localhost:4002
STRIPE_API_URL=http://localhost:4009

# Official emulators
FIREBASE_AUTH_EMULATOR_HOST=127.0.0.1:9099
FIRESTORE_EMULATOR_HOST=127.0.0.1:8080
FIREBASE_STORAGE_EMULATOR_HOST=127.0.0.1:9199
AZURE_STORAGE_CONNECTION_STRING=UseDevelopmentStorage=true
PUBSUB_EMULATOR_HOST=127.0.0.1:8085
GCLOUD_PROJECT=demo-baseline

Baseline’s --state and snapshots cover Baseline’s services only. The Firebase Emulator Suite has its own --import and --export-on-exit, and Azurite keeps its data in the --location folder.

Getting started

Configuration

Custom emulators

Reference

Official emulators

Firebase

Azure Blob Storage

Google Cloud Pub/Sub

Running them together

​Firebase

​Azure Blob Storage

​Google Cloud Pub/Sub

​Running them together

Firebase

Azure Blob Storage

Google Cloud Pub/Sub

Running them together