Connect your app to the Cloud Firestore Emulator

Before connecting your app to the Cloud Firestore emulator, make sure that you understand the overall Firebase Local Emulator Suite workflow and that you install and configure the Local Emulator Suite.

Instrument your app to talk to the emulators

Android, iOS, and Web SDKs

Set up your in-app configuration or test classes to interact with Cloud Firestore as follows.

Android

// 10.0.2.2 is the special IP address to connect to the 'localhost' of
// the host computer from an Android emulator.
FirebaseFirestoreSettings settings = new FirebaseFirestoreSettings.Builder()
        .setHost("10.0.2.2:8080")
        .setSslEnabled(false)
        .setPersistenceEnabled(false)
        .build();

FirebaseFirestore firestore = FirebaseFirestore.getInstance();
firestore.setFirestoreSettings(settings);EmulatorSuite.java

iOS - Swift

let settings = Firestore.firestore().settings
settings.host = "localhost:8080"
settings.isPersistenceEnabled = false 
settings.isSSLEnabled = false
Firestore.firestore().settings = settingsViewController.swift

Web

// Initialize your Web app as described in the Get started for Web
// firebaseApp previously initialized using firebase.initializeApp().
var db = firebaseApp.firestore();
if (location.hostname === "localhost") {
  db.settings({
    host: "localhost:8080",
    ssl: false
  });
}emulator-suite.js

No additional setup is needed to test Cloud Functions triggered by Firestore events using the emulator. When the Firestore and Cloud Functions emulators are both running, they automatically work together.

Admin SDKs

The Firebase Admin SDKs automatically connect to the Cloud Firestore emulator when the FIRESTORE_EMULATOR_HOST environment variable is set:

export FIRESTORE_EMULATOR_HOST="localhost:8080"

Clear your database between tests

Production Firestore provides no platform SDK method for flushing the database, but the Firestore emulator gives you a REST endpoint specifically for this purpose, which can be called from a test framework setup/tearDown step, from a test class, or from the shell (e.g., with curl) before a test is kicked off. You can use this approach as an alternative to simply shutting down the emulator process.

In an appropriate method, perform an HTTP DELETE operation, supplying your Firebase projectID, for example firestore-emulator-example, to the following endpoint:

"http://localhost:8080/emulator/v1/projects/firestore-emulator-example/databases/(default)/documents"

Naturally, your code should await REST confirmation that the flush finished or failed.

You can perform this operation from the shell:

// Shell alternative…
$ curl -v -X DELETE "http://localhost:8080/emulator/v1/projects/firestore-emulator-example/databases/(default)/documents"

Having implemented a step like this, you can sequence your tests and trigger your functions with confidence that old data will be purged between runs and you're using a fresh baseline test configuration.

Import and export data

The Cloud Firestore emulator allows you to export data from a running emulator instance. Define a baseline set of data to use in your unit tests or continuous integration workflows, then export it to be shared among the team.

firebase emulators:export ./dir

In tests, on emulator startup, import the baseline data.

firebase emulators:start --import=./dir

Visualize Security Rules activity

As you work through prototype and test loops, you can use visualization tools and reports provided by the Local Emulator Suite.

Visualize Rules evaluations

As you add Security Rules to your prototype you can debug them with Local Emulator Suite debug tools.

After running a suite of tests, you can access test coverage reports that show how each of your security rules was evaluated.

To get the reports, query an exposed endpoint on the emulator while it's running. For a browser-friendly version, use the following URL:

http://localhost:8080/emulator/v1/projects/<database_name>:ruleCoverage.html

This breaks your rules into expressions and subexpressions that you can mouseover for more information, including number of evaluations and values returned. For the raw JSON version of this data, include the following URL in your query:

http://localhost:8080/emulator/v1/projects/<database_name>:ruleCoverage

Here, the HTML version of the report highlights evaluations that throw undefined and null-value errors:

What next?

For a curated set of videos and detailed how-to examples, follow the Firebase Emulators Training Playlist.
Investigate advanced use cases involving Security Rules testing and the Firebase Test SDK: Test Security Rules (Firestore)
Since triggered functions are a typical integration with Cloud Firestore, learn more about the Cloud Functions for Firebase emulator at Run functions locally.