diff --git a/example/android/app/build.gradle b/example/android/app/build.gradle
index 45c557f..39f8f07 100644
--- a/example/android/app/build.gradle
+++ b/example/android/app/build.gradle
@@ -1,5 +1,8 @@
 plugins {
     id "com.android.application"
+    // START: FlutterFire Configuration
+    id 'com.google.gms.google-services'
+    // END: FlutterFire Configuration
     id "kotlin-android"
     // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
     id "dev.flutter.flutter-gradle-plugin"
@@ -8,7 +11,7 @@ plugins {
 android {
     namespace = "com.example.phone_auth_handler_demo"
     compileSdk = flutter.compileSdkVersion
-    ndkVersion = flutter.ndkVersion
+    ndkVersion = flutter.ndkVersion // ndkVersion = "29.0.14206865"
 
     compileOptions {
         sourceCompatibility = JavaVersion.VERSION_1_8
@@ -24,7 +27,7 @@ android {
         applicationId = "com.example.phone_auth_handler_demo"
         // You can update the following values to match your application needs.
         // For more information, see: https://flutter.dev/to/review-gradle-config.
-        minSdk = 23
+        minSdkVersion = flutter.minSdkVersion
         targetSdk = flutter.targetSdkVersion
         versionCode = flutter.versionCode
         versionName = flutter.versionName
diff --git a/example/android/build.gradle b/example/android/build.gradle
index 4365010..d2ffbff 100644
--- a/example/android/build.gradle
+++ b/example/android/build.gradle
@@ -1,11 +1,3 @@
-buildscript {
-    dependencies {
-        classpath 'com.android.tools.build:gradle:4.1.0'
-        classpath 'com.google.gms:google-services:4.3.10'
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-    }
-}
-
 allprojects {
     repositories {
         google()
diff --git a/example/android/gradle/wrapper/gradle-wrapper.properties b/example/android/gradle/wrapper/gradle-wrapper.properties
index 7bb2df6..9470727 100644
--- a/example/android/gradle/wrapper/gradle-wrapper.properties
+++ b/example/android/gradle/wrapper/gradle-wrapper.properties
@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.14-all.zip
\ No newline at end of file
diff --git a/example/android/settings.gradle b/example/android/settings.gradle
index b9e43bd..7236bcd 100644
--- a/example/android/settings.gradle
+++ b/example/android/settings.gradle
@@ -18,8 +18,11 @@ pluginManagement {
 
 plugins {
     id "dev.flutter.flutter-plugin-loader" version "1.0.0"
-    id "com.android.application" version "8.1.0" apply false
-    id "org.jetbrains.kotlin.android" version "1.8.22" apply false
+    id "com.android.application" version "8.11.0" apply false
+    // START: FlutterFire Configuration
+    id "com.google.gms.google-services" version "4.3.15" apply false
+    // END: FlutterFire Configuration
+    id "org.jetbrains.kotlin.android" version "2.2.20" apply false
 }
 
 include ":app"
diff --git a/example/lib/utils/app_theme.dart b/example/lib/utils/app_theme.dart
index 4a7f6e6..202e2f2 100644
--- a/example/lib/utils/app_theme.dart
+++ b/example/lib/utils/app_theme.dart
@@ -56,7 +56,7 @@ class AppTheme {
       //   selectionColor: accentColor?.withOpacity(0.75),
       //   selectionHandleColor: accentColor?.withOpacity(0.75),
       // ),
-      dialogTheme: DialogTheme(
+      dialogTheme: DialogThemeData(
         elevation: _defaultElevation,
         shape: RoundedRectangleBorder(
           borderRadius: BorderRadius.circular(15),
diff --git a/example/pubspec.yaml b/example/pubspec.yaml
index 1fd2109..d436d31 100644
--- a/example/pubspec.yaml
+++ b/example/pubspec.yaml
@@ -12,15 +12,15 @@ dependencies:
   flutter:
     sdk: flutter
 
-  pinput: ^5.0.0
-  firebase_core: ^3.6.0
-  easy_container: ^1.0.5
+  pinput: ^6.0.2
+  firebase_core: ^4.7.0
+  easy_container: ^1.0.5+1
   intl_phone_field: ^3.2.0
   firebase_phone_auth_handler:
     path: "../"
 
 dev_dependencies:
-  flutter_lints: ^5.0.0
+  flutter_lints: ^6.0.0
 
 
 flutter:
diff --git a/lib/src/auth_controller.dart b/lib/src/auth_controller.dart
index 077199d..ebb8095 100644
--- a/lib/src/auth_controller.dart
+++ b/lib/src/auth_controller.dart
@@ -1,18 +1,21 @@
 part of 'auth_handler.dart';
 
 class FirebasePhoneAuthController extends ChangeNotifier {
+  /// Internal constructor for injection.
+  FirebasePhoneAuthController({FirebaseAuth? auth})
+      : _auth = auth ?? FirebaseAuth.instance;
+
+  final FirebaseAuth _auth;
+
   static FirebasePhoneAuthController _of(
-    BuildContext context, {
-    bool listen = true,
-  }) =>
+      BuildContext context, {
+        bool listen = true,
+      }) =>
       Provider.of<FirebasePhoneAuthController>(context, listen: listen);
 
   /// {@macro autoRetrievalTimeOutDuration}
   static const kAutoRetrievalTimeOutDuration = Duration(minutes: 1);
 
-  /// Firebase auth instance using the default [FirebaseApp].
-  static final FirebaseAuth _auth = FirebaseAuth.instance;
-
   /// Web confirmation result for OTP.
   ConfirmationResult? _webConfirmationResult;
 
@@ -93,7 +96,7 @@ class FirebasePhoneAuthController extends ChangeNotifier {
   /// button, to let user request a new OTP.
   Duration get otpExpirationTimeLeft {
     final otpTickDuration = Duration(
-      seconds: (_otpExpirationTimer?.tick ?? 0),
+      seconds: _otpExpirationTimer?.tick ?? 0,
     );
     return _otpExpirationDuration - otpTickDuration;
   }
@@ -106,7 +109,7 @@ class FirebasePhoneAuthController extends ChangeNotifier {
   /// the OTP, and requires user to manually enter it.
   Duration get autoRetrievalTimeLeft {
     final otpTickDuration = Duration(
-      seconds: (_otpAutoRetrievalTimer?.tick ?? 0),
+      seconds: _otpAutoRetrievalTimer?.tick ?? 0,
     );
     return _autoRetrievalTimeOutDuration - otpTickDuration;
   }
@@ -143,7 +146,7 @@ class FirebasePhoneAuthController extends ChangeNotifier {
     try {
       if (kIsWeb) {
         final userCredential = await _webConfirmationResult!.confirm(otp);
-        return await _loginUser(
+        return _loginUser(
           userCredential: userCredential,
           autoVerified: false,
         );
@@ -152,7 +155,7 @@ class FirebasePhoneAuthController extends ChangeNotifier {
           verificationId: _verificationId!,
           smsCode: otp,
         );
-        return await _loginUser(
+        return _loginUser(
           authCredential: credential,
           autoVerified: false,
         );
@@ -181,16 +184,18 @@ class FirebasePhoneAuthController extends ChangeNotifier {
   /// code send callback to be fired, and [sendOTP] will complete only after
   /// that callback is fired. Not applicable on web.
   Future<bool> sendOTP({bool shouldAwaitCodeSend = true}) async {
+    if (_phoneNumber == null) return false;
+
     Completer? codeSendCompleter;
 
     codeSent = false;
     await Future.delayed(Duration.zero, notifyListeners);
 
-    verificationCompletedCallback(AuthCredential authCredential) async {
+    void verificationCompletedCallback(AuthCredential authCredential) async {
       await _loginUser(authCredential: authCredential, autoVerified: true);
     }
 
-    verificationFailedCallback(FirebaseAuthException authException) {
+    void verificationFailedCallback(FirebaseAuthException authException) {
       final stackTrace = authException.stackTrace ?? StackTrace.current;
 
       if (codeSendCompleter != null && !codeSendCompleter.isCompleted) {
@@ -199,10 +204,10 @@ class FirebasePhoneAuthController extends ChangeNotifier {
       _onLoginFailed?.call(authException, stackTrace);
     }
 
-    codeSentCallback(
-      String verificationId, [
-      int? forceResendingToken,
-    ]) async {
+    Future<void> codeSentCallback(
+        String verificationId, [
+          int? forceResendingToken,
+        ]) async {
       _verificationId = verificationId;
       _forceResendingToken = forceResendingToken;
       codeSent = true;
@@ -213,7 +218,7 @@ class FirebasePhoneAuthController extends ChangeNotifier {
       _setTimer();
     }
 
-    codeAutoRetrievalTimeoutCallback(String verificationId) {
+    void codeAutoRetrievalTimeoutCallback(String verificationId) {
       _verificationId = verificationId;
     }
 
@@ -309,7 +314,7 @@ class FirebasePhoneAuthController extends ChangeNotifier {
   void _setTimer() {
     _otpExpirationTimer = Timer.periodic(
       const Duration(seconds: 1),
-      (timer) {
+          (timer) {
         if (timer.tick == _otpExpirationDuration.inSeconds) {
           _otpExpirationTimer?.cancel();
         }
@@ -320,7 +325,7 @@ class FirebasePhoneAuthController extends ChangeNotifier {
     );
     _otpAutoRetrievalTimer = Timer.periodic(
       const Duration(seconds: 1),
-      (timer) {
+          (timer) {
         if (timer.tick == _autoRetrievalTimeOutDuration.inSeconds) {
           _otpAutoRetrievalTimer?.cancel();
         }
diff --git a/lib/src/auth_handler.dart b/lib/src/auth_handler.dart
index 74ea0e7..6862f33 100644
--- a/lib/src/auth_handler.dart
+++ b/lib/src/auth_handler.dart
@@ -182,12 +182,12 @@ class FirebasePhoneAuthHandler extends StatefulWidget {
 class _FirebasePhoneAuthHandlerState extends State<FirebasePhoneAuthHandler> {
   @override
   void initState() {
-    (() async {
+    unawaited(() async {
       final con = FirebasePhoneAuthController._of(context, listen: false);
 
       RecaptchaVerifier? captcha;
-      if (widget.recaptchaVerifierForWebProvider != null) {
-        captcha = widget.recaptchaVerifierForWebProvider!(kIsWeb);
+      if (kIsWeb && widget.recaptchaVerifierForWebProvider != null) {
+        captcha = widget.recaptchaVerifierForWebProvider!(true);
       }
 
       con._setData(
@@ -204,7 +204,7 @@ class _FirebasePhoneAuthHandlerState extends State<FirebasePhoneAuthHandler> {
       );
 
       if (widget.sendOtpOnInitialize) await con.sendOTP();
-    })();
+    }());
     super.initState();
   }
 
diff --git a/lib/src/auth_provider.dart b/lib/src/auth_provider.dart
index d7fd0a4..ddca721 100644
--- a/lib/src/auth_provider.dart
+++ b/lib/src/auth_provider.dart
@@ -1,3 +1,4 @@
+import 'package:firebase_auth/firebase_auth.dart';
 import 'package:firebase_phone_auth_handler/src/auth_handler.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
@@ -8,15 +9,19 @@ class FirebasePhoneAuthProvider extends StatelessWidget {
   const FirebasePhoneAuthProvider({
     super.key,
     required this.child,
+    this.auth,
   });
 
   /// The child of the widget.
   final Widget child;
 
+  /// The [FirebaseAuth] instance to use.
+  final FirebaseAuth? auth;
+
   @override
   Widget build(BuildContext context) {
     return ChangeNotifierProvider<FirebasePhoneAuthController>(
-      create: (_) => FirebasePhoneAuthController(),
+      create: (_) => FirebasePhoneAuthController(auth: auth),
       child: child,
     );
   }
diff --git a/pubspec.yaml b/pubspec.yaml
index 9d7988e..ea0f689 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -26,11 +26,15 @@ dependencies:
   flutter:
     sdk: flutter
 
-  provider: ^6.1.2
-  firebase_auth: ^5.3.1
+  provider: ^6.1.5+1
+  firebase_auth: ^6.4.0
 
 dev_dependencies:
-  flutter_lints: ^5.0.0
+  flutter_test:
+    sdk: flutter
+  flutter_lints: ^6.0.0
+  mocktail: ^1.0.5
+  firebase_auth_mocks: ^0.15.1
 
 false_secrets:
   - /example/android/app/google-services.json
diff --git a/test/firebase_phone_auth_controller_test.dart b/test/firebase_phone_auth_controller_test.dart
new file mode 100644
index 0000000..c5ef374
--- /dev/null
+++ b/test/firebase_phone_auth_controller_test.dart
@@ -0,0 +1,55 @@
+
+import 'package:firebase_phone_auth_handler/firebase_phone_auth_handler.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+
+import 'mocks.dart';
+
+void main() {
+  late MockFirebaseAuth auth;
+  late FirebasePhoneAuthController controller;
+
+  setUpAll(() {
+    registerFallbackValue(MockAuthCredential());
+    registerFallbackValue(MockFirebaseAuthException());
+    registerFallbackValue(const Duration(seconds: 30));
+  });
+
+  setUp(() {
+    auth = MockFirebaseAuth();
+    when(() => auth.signOut()).thenAnswer((_) async => {});
+    controller = FirebasePhoneAuthController(auth: auth);
+  });
+
+  group('FirebasePhoneAuthController - Verification Logic', () {
+    test('sendOTP fails if phoneNumber is not set', () async {
+      // Expect error or false because _phoneNumber is null initially
+      final result = await controller.sendOTP();
+      expect(result, isFalse);
+    });
+
+    test('verifyOtp returns false if verificationId is missing', () async {
+      final result = await controller.verifyOtp('123456');
+      expect(result, isFalse);
+    });
+  });
+
+  group('FirebasePhoneAuthController - Basic State', () {
+    test('initial state is correct', () {
+      expect(controller.codeSent, isFalse);
+      expect(controller.isSendingCode, isTrue);
+      expect(controller.isOtpExpired, isTrue);
+    });
+
+    test('clear() resets state', () {
+      controller.clear();
+      expect(controller.codeSent, isFalse);
+      expect(controller.isOtpExpired, isTrue);
+    });
+
+    test('signOut() calls firebase auth signOut', () async {
+      await controller.signOut();
+      verify(() => auth.signOut()).called(1);
+    });
+  });
+}
diff --git a/test/firebase_phone_auth_handler_test.dart b/test/firebase_phone_auth_handler_test.dart
new file mode 100644
index 0000000..b1b4e6a
--- /dev/null
+++ b/test/firebase_phone_auth_handler_test.dart
@@ -0,0 +1,183 @@
+import 'package:firebase_auth/firebase_auth.dart';
+import 'package:firebase_phone_auth_handler/firebase_phone_auth_handler.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+
+import 'mocks.dart';
+
+void main() {
+  late MockFirebaseAuth auth;
+
+  setUpAll(() {
+    registerFallbackValue(MockAuthCredential());
+    registerFallbackValue(MockFirebaseAuthException());
+    registerFallbackValue(const Duration(seconds: 30));
+  });
+
+  setUp(() {
+    auth = MockFirebaseAuth();
+    when(() => auth.signOut()).thenAnswer((_) async => {});
+  });
+
+  testWidgets('FirebasePhoneAuthHandler triggers onCodeSent when OTP is sent',
+      (WidgetTester tester) async {
+    bool codeSentCalled = false;
+
+    // Mock verifyPhoneNumber to trigger codeSent callback
+    when(() => auth.verifyPhoneNumber(
+          phoneNumber: any(named: 'phoneNumber'),
+          verificationCompleted: any(named: 'verificationCompleted'),
+          verificationFailed: any(named: 'verificationFailed'),
+          codeSent: any(named: 'codeSent'),
+          codeAutoRetrievalTimeout: any(named: 'codeAutoRetrievalTimeout'),
+          timeout: any(named: 'timeout'),
+          forceResendingToken: any(named: 'forceResendingToken'),
+        )).thenAnswer((invocation) async {
+      final codeSentCallback =
+          invocation.namedArguments[#codeSent] as PhoneCodeSent;
+      codeSentCallback('test-ver-id', 123);
+    });
+
+    await tester.pumpWidget(
+      FirebasePhoneAuthProvider(
+        auth: auth,
+        child: MaterialApp(
+          home: Scaffold(
+            body: FirebasePhoneAuthHandler(
+              phoneNumber: '+1234567890',
+              sendOtpOnInitialize: true,
+              onCodeSent: () {
+                codeSentCalled = true;
+              },
+              builder: (context, controller) {
+                return Text(controller.codeSent ? 'CODE_SENT' : 'SENDING');
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    // Initial pump might not trigger the async callback immediately
+    await tester.pumpAndSettle();
+
+    expect(codeSentCalled, isTrue);
+    expect(find.text('CODE_SENT'), findsOneWidget);
+  });
+
+  testWidgets(
+      'FirebasePhoneAuthHandler triggers onLoginSuccess on verification success',
+      (WidgetTester tester) async {
+    UserCredential? successCredential;
+    final mockUserCredential = MockUserCredential();
+    final mockUser = MockUser();
+    when(() => mockUserCredential.user).thenReturn(mockUser);
+
+    // Mock verifyPhoneNumber to trigger codeSent
+    when(() => auth.verifyPhoneNumber(
+          phoneNumber: any(named: 'phoneNumber'),
+          verificationCompleted: any(named: 'verificationCompleted'),
+          verificationFailed: any(named: 'verificationFailed'),
+          codeSent: any(named: 'codeSent'),
+          codeAutoRetrievalTimeout: any(named: 'codeAutoRetrievalTimeout'),
+          timeout: any(named: 'timeout'),
+          forceResendingToken: any(named: 'forceResendingToken'),
+        )).thenAnswer((invocation) async {
+      final codeSentCallback =
+          invocation.namedArguments[#codeSent] as PhoneCodeSent;
+      codeSentCallback('test-ver-id', 123);
+    });
+
+    // Mock signInWithCredential for manual verification
+    when(() => auth.signInWithCredential(any()))
+        .thenAnswer((_) async => mockUserCredential);
+
+    await tester.pumpWidget(
+      FirebasePhoneAuthProvider(
+        auth: auth,
+        child: MaterialApp(
+          home: Scaffold(
+            body: FirebasePhoneAuthHandler(
+              phoneNumber: '+1234567890',
+              sendOtpOnInitialize: true,
+              onLoginSuccess: (credential, autoVerified) {
+                successCredential = credential;
+              },
+              builder: (context, controller) {
+                return ElevatedButton(
+                  onPressed: () => controller.verifyOtp('123456'),
+                  child: const Text('VERIFY'),
+                );
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    await tester.pumpAndSettle(); // Wait for codeSent
+    await tester.tap(find.text('VERIFY'));
+    await tester.pumpAndSettle();
+
+    expect(successCredential, isNotNull);
+    verify(() => auth.signInWithCredential(any())).called(1);
+  });
+
+  testWidgets(
+      'FirebasePhoneAuthHandler triggers onLoginFailed on verification failure',
+      (WidgetTester tester) async {
+    FirebaseAuthException? loginException;
+
+    // Mock verifyPhoneNumber to trigger codeSent
+    when(() => auth.verifyPhoneNumber(
+          phoneNumber: any(named: 'phoneNumber'),
+          verificationCompleted: any(named: 'verificationCompleted'),
+          verificationFailed: any(named: 'verificationFailed'),
+          codeSent: any(named: 'codeSent'),
+          codeAutoRetrievalTimeout: any(named: 'codeAutoRetrievalTimeout'),
+          timeout: any(named: 'timeout'),
+          forceResendingToken: any(named: 'forceResendingToken'),
+        )).thenAnswer((invocation) async {
+      final codeSentCallback =
+          invocation.namedArguments[#codeSent] as PhoneCodeSent;
+      codeSentCallback('test-ver-id', 123);
+    });
+
+    // Mock signInWithCredential to throw FirebaseAuthException
+    final mockException = MockFirebaseAuthException();
+    when(() => mockException.code).thenReturn('invalid-verification-code');
+    when(() => mockException.message).thenReturn('The code is invalid.');
+    when(() => auth.signInWithCredential(any())).thenThrow(mockException);
+
+    await tester.pumpWidget(
+      FirebasePhoneAuthProvider(
+        auth: auth,
+        child: MaterialApp(
+          home: Scaffold(
+            body: FirebasePhoneAuthHandler(
+              phoneNumber: '+1234567890',
+              sendOtpOnInitialize: true,
+              onLoginFailed: (exception, stackTrace) {
+                loginException = exception;
+              },
+              builder: (context, controller) {
+                return ElevatedButton(
+                  onPressed: () => controller.verifyOtp('000000'),
+                  child: const Text('VERIFY_FAIL'),
+                );
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('VERIFY_FAIL'));
+    await tester.pumpAndSettle();
+
+    expect(loginException, isNotNull);
+    expect(loginException!.code, 'invalid-verification-code');
+  });
+}
diff --git a/test/mocks.dart b/test/mocks.dart
new file mode 100644
index 0000000..232cc03
--- /dev/null
+++ b/test/mocks.dart
@@ -0,0 +1,16 @@
+import 'package:firebase_auth/firebase_auth.dart';
+import 'package:mocktail/mocktail.dart';
+
+class MockFirebaseAuth extends Mock implements FirebaseAuth {}
+
+class MockConfirmationResult extends Mock implements ConfirmationResult {}
+
+class MockAuthCredential extends Mock implements AuthCredential {}
+
+class MockPhoneAuthCredential extends Mock implements PhoneAuthCredential {}
+
+class MockUserCredential extends Mock implements UserCredential {}
+
+class MockUser extends Mock implements User {}
+
+class MockFirebaseAuthException extends Mock implements FirebaseAuthException {}