context doesn't match when testing Provider

Question

I have written a test to check that a provider works as expected, however i get the following exception when checking that the context matches the providers context:

══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following TestFailure object was thrown running a test:
  Expected:
_InheritedProvderElement<AuthScreen>:<ChangeNotifierProvider<AuthScreen>-[GlobalKey#11403](value:
Instance of 'AuthScreen', listening to value)>
  Actual:
_DefaultInheritedProviderScopeElement<AuthScreen>:<_DefaultInheritedProviderScope<AuthScreen>(value:
Instance of 'AuthScreen', listening to value)>

When the exception was thrown, this was the stack:
#4      main.<anonymous closure> (file:///home/hannes/Documents/StudioProjects/brf/test/Authentication/authenticate_test.dart:24:5)
<asynchronous suspension>
#5      testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test/src/widget_tester.dart:140:29)
<asynchronous suspension>
#6      TestWidgetsFlutterBinding._runTestBody (package:flutter_test/src/binding.dart:699:19)
<asynchronous suspension>
#9      TestWidgetsFlutterBinding._runTest (package:flutter_test/src/binding.dart:679:14)
#10     AutomatedTestWidgetsFlutterBinding.runTest.<anonymous closure> (package:flutter_test/src/binding.dart:1079:24)
#16     AutomatedTestWidgetsFlutterBinding.runTest (package:flutter_test/src/binding.dart:1076:15)
#17     testWidgets.<anonymous closure> (package:flutter_test/src/widget_tester.dart:133:24)
#18     Declarer.test.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/declarer.dart:171:27)
<asynchronous suspension>
#19     Invoker.waitForOutstandingCallbacks.<anonymous closure> (package:test_api/src/backend/invoker.dart:242:15)
#24     Invoker.waitForOutstandingCallbacks (package:test_api/src/backend/invoker.dart:239:5)
#25     Declarer.test.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/declarer.dart:169:33)
#30     Declarer.test.<anonymous closure> (package:test_api/src/backend/declarer.dart:168:13)
#31     Invoker._onRun.<anonymous closure>.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/invoker.dart:392:25)
#45     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:398:19)
#46     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429:5)
#47     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)
(elided 28 frames from class _FakeAsync, package dart:async, package dart:async-patch, and package stack_trace)

This was caught by the test expectation on the following line:
  file:///home/hannes/Documents/StudioProjects/brf/test/Authentication/authenticate_test.dart line 24
The test description was:
  AuthScreen provider changes value
════════════════════════════════════════════════════════════════════════════════════════════════════

Also, _childKey.currentContext is null. I don't know if that is related or if it's something else that I'm doing wrong.

I have tried to follow this guide, and my test looks like this:

import 'package:brf/models/auth_screen.dart';
import 'package:brf/screens/authenticate/authenticate.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() {

  setUp(() {
    AuthScreen();
  });

  testWidgets('AuthScreen provider changes value', (WidgetTester tester) async {
    final _providerKey = GlobalKey();
    final _childKey = GlobalKey();
    BuildContext context;

    await tester.pumpWidget(
      MaterialApp(
        home: ChangeNotifierProvider<AuthScreen>(
          key: _providerKey,
          create: (c) {
            context = c;
            return AuthScreen();
          },
          child: Authenticate(key: _childKey),
        ),
      ),
    );

    expect(context, equals(_providerKey.currentContext));

    expect(Provider.of<AuthScreen>(_childKey.currentContext).showSignIn, true);

    Provider.of<AuthScreen>(context, listen: false).switchScreen();
    await Future.microtask(tester.pump);

    expect(Provider.of<AuthScreen>(_childKey.currentContext).showSignIn, false);
  });
}

And finally AuthScreen looks like this:

import 'package:flutter/material.dart';

class AuthScreen extends ChangeNotifier{
  bool _showSignIn = true;

  bool get showSignIn => _showSignIn;

  void switchScreen(){
    _showSignIn = !_showSignIn;
    notifyListeners();
  }
}

Diwyanshu sharma · Answer 1 · 2020-03-11T12:22:45.277

0

This is the error for the null context you passed

you this one: Builder(builder: (context) => Widget here

Try like this where you want to pass the context:

 MaterialApp(
        home: Builder(builder: (context) => ChangeNotifierProvider<AuthScreen>(
          key: _providerKey,
          create: (c) {
            context = c;
            return AuthScreen();
          },
          child: Authenticate(key: _childKey),
        ),
      ),
    );

edited Mar 11 '20 at 12:22

answered Mar 11 '20 at 11:39

Diwyanshu sharma

121
4

Where should the builder be exactly? Above MaterialApp? – Hannes Hultergård Mar 11 '20 at 12:12
@HannesHultergård, Check now – Diwyanshu sharma Mar 11 '20 at 12:23

context doesn't match when testing Provider

1 Answers1