# Use App Check with the debug provider

If, after you have registered your app for App Check, you want to run your
app in an environment that App Check would normally not classify as valid,
such as a simulator during development, or from a continuous integration (CI)
environment, you can create a debug build of your app that uses the
App Check debug provider instead of App Attest.

<br />

**Firebase users**: You must follow the steps on this page to configure Google Sign-in to use the App Check debug provider, even if you've already configured Firebase services to use the App Check debug provider.

<br />

> [!WARNING]
> **Warning:** The debug provider allows access to your project's auth endpoints from unverified devices. **Don't** use the debug provider in production builds of your app, and be careful not to leak your debug token.

## Use the debug provider in a simulator

To use the debug provider while running your app in a simulator interactively
(during development, for example), do the following:

1. Look up the iOS API key for your project on the [Credentials](https://console.cloud.google.com/apis/credentials?project=_)
   page of the **APIs \& Services** section of the Google Cloud console.

2. In your debug build, configure App Check to use the debug provider. You'll
   need to specify the API key you got in the previous step.

       #if targetEnvironment(simulator)
       GIDSignIn.sharedInstance.configureDebugProvider(withAPIKey: apiKey) { error in
         if let error {
           print("Error configuring `GIDSignIn` for App Check: \(error)")
         }
       }
       #else
       // Configure App Check for production.
       #endif

3. Launch the app. A local debug token will be logged to the Xcode console when
   the SDK tries to send a request to the backend. For example:

       <Warning> [AppCheckCore][I-GAC004001] App Check debug token:
       '123a4567-b89c-12d3-e456-789012345678'.

4. In the [App Check](https://console.firebase.google.com/project/_/appcheck) section
   of the Firebase console, choose **Manage debug tokens** from your app's
   overflow menu. Then, register the debug token you logged in the previous
   step.

   ![Screenshot of the Manage Debug Tokens menu item](https://firebase.google.com/docs/app-check/manage-debug-tokens.png)

After you register the token, Google's OAuth 2.0 endpoints will accept it as
valid for your project.

Because this token allows access to your auth endpoints without a
valid device, it is crucial that you keep it private. Don't commit it to a
public repository, and if a registered token is ever compromised, revoke it
immediately in the Firebase console.

## Use the debug provider in a CI environment

To use the debug provider in a continuous integration (CI) environment, do the
following:

1. In the [App Check](https://console.firebase.google.com/project/_/appcheck) section
   of the Firebase console, choose **Manage debug tokens** from your app's
   overflow menu. Then, create a new debug token. You'll need the token in the
   next step.

   Because this token allows access to your auth endpoints without
   a valid device, it is crucial that you keep it private. Don't commit it to a
   public repository, and if a registered token is ever compromised, revoke it
   immediately in the Firebase console.

   ![Screenshot of the Manage Debug Tokens menu item](https://firebase.google.com/docs/app-check/manage-debug-tokens.png)
2. Add the debug token you just created to your CI system's secure key store
   (for example, GitHub Actions' [encrypted secrets](https://docs.github.com/en/actions/reference/encrypted-secrets)
   or Travis CI's [encrypted variables](https://docs.travis-ci.com/user/environment-variables/#defining-encrypted-variables-in-travisyml)).

3. If necessary, configure your CI system to make your debug token available
   within the CI environment as an environment variable. Name the variable
   something like `APP_CHECK_DEBUG_TOKEN_FROM_CI`.

4. In Xcode, add an environment variable to your testing scheme with the name
   `FIRAAppCheckDebugToken` and something like `$(APP_CHECK_DEBUG_TOKEN)` as
   the value.

5. Configure your CI test script to pass the debug token as an environment
   variable. For example:

   ```
   xcodebuild test -scheme YourTestScheme -workspace YourProject.xcworkspace \
   APP_CHECK_DEBUG_TOKEN=$(APP_CHECK_DEBUG_TOKEN_FROM_CI)
   ```
6. Look up the iOS API key for your project on the [Credentials](https://console.cloud.google.com/apis/credentials?project=_)
   page of the **APIs \& Services** section of the Google Cloud console.

7. In your debug build, configure App Check to use the debug provider. You'll
   need to specify the API key you got in the previous step.

       #if targetEnvironment(simulator)
       GIDSignIn.sharedInstance.configureDebugProvider(withAPIKey: apiKey) { error in
         if let error {
           print("Error configuring `GIDSignIn` for App Check: \(error)")
         }
       }
       #else
       // Configure App Check for production.
       #endif

When your app runs in a CI environment, Google's OAuth 2.0 endpoints will accept
the token it sends as valid for your project.