How to mock 'FirebaseAuth.instance'? - unit-testing

Question

I want to start writing unit test to my flutter app that have developed using GetX pattern. In GetX pattern, the code is separated to controller and view, so all methods that I want to test is in controller.
In my app, I am using firebase to make authentication with mobile number.
This is LoginController:
class LoginController extends GetxService {
...
LoginController(this.authService);
final _auth = FirebaseAuth.instance;
String validatePhoneNumber(String phoneNumber) {
if (!phoneNumber.startsWith('+20')) {
return 'أدخل كود البلد مثل: +20 في مصر';
} else if (phoneNumber.length < 11) {
return 'أدخل رقم صحيح';
} else if (phoneNumber.isEmpty) {
return 'أدخل رقم الهاتف';
}
return null;
}
Future<void> validate() async {
await _auth.verifyPhoneNumber(
phoneNumber: phoneNumberController.text,
timeout: timeoutDuration,
codeAutoRetrievalTimeout: (String verificationId) {
verId.value = verificationId;
currentState.value = SignInPhoneWidgetState.CodeAutoRetrievalTimeout;
},
codeSent: (String verificationId, [int forceResendingToken]) {
verId.value = verificationId;
currentState.value = SignInPhoneWidgetState.CodeSent;
DialogService.to.stopLoading();
Get.toNamed(Routes.ACCEPT_SMS);
},
verificationCompleted: (AuthCredential phoneAuthCredential) async {
currentState.value = SignInPhoneWidgetState.Complete;
try {
if (authService.currentUser.value != null) {
await authService.currentUser.value
.linkWithCredential(phoneAuthCredential);
} else {
await _auth.signInWithCredential(phoneAuthCredential);
}
Get.offAllNamed(Routes.ROOTHOME);
//widget.onLoggedIn(authResult);
} on PlatformException catch (e) {
print(e);
errorCode.value = e.code;
errorMessage.value = e.message;
} catch (e) {
print(e);
} finally {
//.......
}
},
verificationFailed: (FirebaseAuthException error) {
errorCode.value = error.code;
errorMessage.value = error.message;
currentState.value = SignInPhoneWidgetState.Failed;
},
//forceResendingToken:
);
}
Future<void> validateSmsCode() async {
//_auth.
var cred = PhoneAuthProvider.credential(
verificationId: verId.value, smsCode: verifyCodeController.text);
try {
if (authService.currentUser.value != null) {
await authService.currentUser.value.linkWithCredential(cred);
} else {
await _auth.signInWithCredential(cred);
await Get.offAllNamed(Routes.ROOTHOME);
}
} on PlatformException catch (ex) {
errorCode.value = ex.code;
errorMessage.value = ex.message;
currentState.value = SignInPhoneWidgetState.Failed;
} on FirebaseAuthException catch (ex) {
errorCode.value = ex.code;
errorMessage.value = ex.message;
currentState.value = SignInPhoneWidgetState.Failed;
}
}
...
}
This is login_test.dart file:
I should mock every outside operation like firebase. But In this case I want to test validatePhoneNumber method, that checks if the phone number is valid or not. the method it self hasn't firebase operations. But, the method is called by a LoginController object, And this object it self has instance of FirebaseAuth.instance.
final _authSerive = AuthService();
main() async {
final loginController = LoginController(_authSerive);
setUp(() async {});
tearDown(() {});
group('Phone Validation', () {
test('Valid Email', () {
String result = loginController.validatePhoneNumber('[phone]');
expect(result, null);
});
});
}
When I tried to run this test method, This error appeared.
Failed to load "D:\bdaya\ta7t-elbeet-client\test\login_test.dart":
[core/no-app] No Firebase App '[DEFAULT]' has been created - call
Firebase.initializeApp()
The reasen is:
This line in The LoginController:
final _auth = FirebaseAuth.instance;
I certainly know that I have to mock Firebase operations.
How to mock it in this case or, What should I do?