How to wait for a future to complete in Flutter widget test?

Question

I am trying to perform a widget test, specifically navigation test. I am using bloc architecture, setting a stream on the bloc triggers a series of events inside the bloc, gets session info from the server call (which returns a future of session info object), on successful server call a login stream is set and the widget has a stream subscription to this stream and navigates to the next screen.

I am using mockito to mock the server call and stubbing the server call to return a future of success response. The problem is the when I am calling pumpAndSettle() it is getting timed out as it is not waiting for the future to complete and return the success response.

I apologize if I am not making it very clear, but here is the sample code:

login_bloc.dart

class LoginBloc {
  LoginRepository _loginRepository;
  final String searchKeyword = "special-keyword";

  final _urlString = PublishSubject<String>();
  final _isLoggedIn = BehaviorSubject<bool>(seedValue: false);
  final _errorMessage = PublishSubject<String>();

  Observable<bool> get isLoggedIn => _isLoggedIn.stream;
  Observable<String> get isErrorState => _errorMessage.stream;

  LoginBloc({LoginRepository loginRepository})
      : _loginRepository = loginRepository ?? LoginRepository() {
          // Listen on the _urlString stream to call the function which checks for the special keyword and if a match is found make a server call
    _urlString.stream.listen((String url) {
      _authorizationFullService(url);
    });
  }

    // Search for special keyword and if a match is found call the server call function
  void _authorizationFullService(String url) {
    if (url.contains(searchKeyword)) {
      int index = url.indexOf(searchKeyword);
      String result = url.substring(index + searchKeyword.length);
      result = result.trim();
      String decodedUrl = Uri.decodeFull(result);
      if (decodedUrl != null && decodedUrl.length > 0) {
        _fullServiceServerCall(decodedUrl);
      } else {
        _isLoggedIn.sink.add(false);
      }
    }
  }

    // Call server call function from repository which returns a future of the Authorization object
  void _fullServiceServerCall(String decodedUrl) {
    _loginRepository
        .getSession(decodedUrl)
        .then(_handleSuccessAuthorization)
        .catchError(_handleErrorState);
  }

    // Handle success response and set the login stream
  void _handleSuccessAuthorization(Authorization authorization) {
    if (authorization != null && authorization.idnumber != 0) {
      _isLoggedIn.sink.add(true);
    } else {
      _isLoggedIn.sink.add(false);
    }
  }

    // Handle error response and set the error stream
  void _handleErrorState(dynamic error) {
    _isLoggedIn.sink.add(false);
    _errorMessage.sink.add(error.toString());
  }

  void dispose() {
    _urlString.close();
    _isLoggedIn.close();
    _errorMessage.close();
  }
}

widget_test.dart

group('Full Login Navigation test', () {
    LoginRepository mockLoginRepository;
    LoginBloc loginBloc;
    NotificationBloc notificationBloc;
    NavigatorObserver mockNavigatorObserver;
    Authorization _auth;
    String testUrl;

    setUp(() {
      mockLoginRepository = MockLoginRepository();
      _auth = Authorization((auth) => auth
        ..param1 = "foo"
        ..param2 = "bar"
        ..param3 = "foobar"
        ..param4 = "barfoo");
      loginBloc = LoginBloc(loginRepository: mockLoginRepository);
      mockNavigatorObserver = MockNavigatorObserver();
      testUrl = "http://test.test.com";
    });

    Future<Null> _buildFullLoginPage(LoginBloc loginBloc,
        NotificationBloc notificationBloc, WidgetTester tester) async {
      when(mockLoginRepository.getSession(testUrl))
          .thenAnswer((_) => Future.value(_auth));
      await tester.pumpWidget(LoginBlocProvider(
        child: NotificationBlocProvider(
          child: MaterialApp(
            home: LoginFullService(),
            onGenerateRoute: NavigationRoutes.routes,
            navigatorObservers: [mockNavigatorObserver],
          ),
          notificationBloc: notificationBloc,
        ),
        loginBloc: loginBloc,
      ));
      //TODO: Remove casting to dynamic after dart sdk bug fix: https://github.com/dart-lang/mockito/issues/163
      verify(mockNavigatorObserver.didPush(any, any) as dynamic);
      loginBloc.getAuthorization(
          "http://testing.testing.com?search-keyword=http%3A%2F%2Ftest.test.com");
    }

    testWidgets('Navigate to landing page on correct login url',
        (WidgetTester tester) async {
      await _buildFullLoginPage(loginBloc, notificationBloc, tester);
      await tester.pumpAndSettle();
      expect(find.byKey(Key('webview_scaffold')), findsNothing);
      //TODO: Remove casting to dynamic after dart sdk bug fix: https://github.com/dart-lang/mockito/issues/163
      verify(mockNavigatorObserver.didPush(any, any) as dynamic);
    });
});

On running the widget test the tester.pumpAndSettle() inside testWidgets times out before the future is completed. This is the error log:

══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following assertion was thrown running a test:
pumpAndSettle timed out

When the exception was thrown, this was the stack:
#0      WidgetTester.pumpAndSettle.<anonymous closure> (package:flutter_test/src/widget_tester.dart:299:11)
<asynchronous suspension>
#3      TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:69:41)
#4      WidgetTester.pumpAndSettle (package:flutter_test/src/widget_tester.dart:295:27)
#5      main.<anonymous closure>.<anonymous closure> (file:///Users/ssiddh/Documents/projects/mobile-flutter/test/ui/pages/login/login_full_test.dart:114:20)
<asynchronous suspension>
#6      testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test/src/widget_tester.dart:72:23)
#7      TestWidgetsFlutterBinding._runTestBody (package:flutter_test/src/binding.dart:555:19)
<asynchronous suspension>
#10     TestWidgetsFlutterBinding._runTest (package:flutter_test/src/binding.dart:539:14)
#11     AutomatedTestWidgetsFlutterBinding.runTest.<anonymous closure> (package:flutter_test/src/binding.dart:883:24)
#17     AutomatedTestWidgetsFlutterBinding.runTest (package:flutter_test/src/binding.dart:880:15)
#18     testWidgets.<anonymous closure> (package:flutter_test/src/widget_tester.dart:71:22)
#19     Declarer.test.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test/src/backend/declarer.dart:168:27)
<asynchronous suspension>
#20     Invoker.waitForOutstandingCallbacks.<anonymous closure> (package:test/src/backend/invoker.dart:249:15)
<asynchronous suspension>
#25     Invoker.waitForOutstandingCallbacks (package:test/src/backend/invoker.dart:246:5)
#26     Declarer.test.<anonymous closure>.<anonymous closure> (package:test/src/backend/declarer.dart:166:33)
#31     Declarer.test.<anonymous closure> (package:test/src/backend/declarer.dart:165:13)
<asynchronous suspension>
#32     Invoker._onRun.<anonymous closure>.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test/src/backend/invoker.dart:403:25)
<asynchronous suspension>
#46     _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382:19)
#47     _Timer._handleMessage (dart:isolate/runtime/libtimer_impl.dart:416:5)
#48     _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:169:12)
(elided 30 frames from class _FakeAsync, package dart:async, and package stack_trace)

I would really appreciate any kind of help or feedback.

Answer 1

Try wrapping your test with

testWidgets('Navigate to landing page on correct login url',
    (WidgetTester tester) async {
    await tester.runAsync(() async {

      // test code here

    });
 });