chore(auth): Add celest_test helper for email OTP events

packages/celest_test/lib/celest_test.dart

@@ -35,8 +35,35 @@ final class CelestTester {
 
   final VmService _vmService;
 
+  /// Auth-related test helpers.
+  late final CelestAuthTester auth = CelestAuthTester._(_vmService);
+
   /// Closes the connection to the VM service.
   Future<void> close() async {
     await _vmService.dispose();
   }
 }
+
+/// An OTP code sent by the server.
+typedef Otp = ({String to, String code});
+
+/// A helper class for running integration tests with Celest Auth.
+final class CelestAuthTester {
+  CelestAuthTester._(this._vmService);
+
+  final VmService _vmService;
+
+  /// OTP codes sent to users during sign up/sign in.
+  Stream<Otp> get onSentOtp async* {
+    await for (final event in _vmService.onExtensionEvent) {
+      if (event.extensionKind != 'celest.cloud_auth.emailOtpSent') {
+        continue;
+      }
+      final data = event.extensionData!.data;
+      yield (
+        to: data['to'] as String,
+        code: data['code'] as String,
+      );
+    }
+  }
+}

services/celest_cloud_auth/lib/src/email/email_provider.dart

@@ -1,3 +1,5 @@
+import 'dart:developer' as developer;
+
 import 'package:celest_cloud_auth/src/context.dart';
 import 'package:celest_cloud_auth/src/otp/otp_provider.dart';
 
@@ -7,6 +9,7 @@ extension type const EmailOtpProvider._(OtpSender _send) implements Object {
   const EmailOtpProvider([OtpSender send = _defaultSend]) : this._(send);
 
   static Future<void> _defaultSend(Otp message) async {
+    developer.postEvent('celest.cloud_auth.emailOtpSent', message.toJson());
     context.logger.info('Verification code for ${message.to}: ${message.code}');
   }
 

services/celest_cloud_auth/lib/src/otp/otp_provider.dart

@@ -3,4 +3,8 @@ typedef Otp = ({
   String code,
 });
 
+extension OtpX on Otp {
+  Map<String, Object?> toJson() => {'to': to, 'code': code};
+}
+
 typedef OtpSender = Future<void> Function(Otp);