Testing shared_preferences on flutter

You needed to mock getAll from shared_preferences (ref: https://pub.dartlang.org/packages/shared_preferences)

Here's the sample code:

import 'package:shared_preferences/shared_preferences.dart';
import 'package:flutter/services.dart'; // <-- needed for `MethodChannel`

void main() {

  setUpAll(() {
    const MethodChannel('plugins.flutter.io/shared_preferences')
        .setMockMethodCallHandler((MethodCall methodCall) async {
      if (methodCall.method == 'getAll') {
        return <String, dynamic>{}; // set initial values here if desired
      }
      return null;
    });
  });

  testWidgets('Click on login saves the credentials',
      (WidgetTester tester) async {
    await tester.pumpWidget(MyApp());

    await tester.enterText(find.byKey(Key('phoneInput')), 'test');
    await tester.enterText(find.byKey(Key('passwordInput')), 'test');
    await tester.tap(find.byIcon(Icons.lock));

    SharedPreferences prefs = await SharedPreferences.getInstance();
    expect(prefs.getString('phone'), 'test');
    expect(prefs.getString('password'), 'test');
  });
}

Original answer:

testWidgets('Click on login saves the credentials',
      (WidgetTester tester) async {
      final AutomatedTestWidgetsFlutterBinding binding = tester.binding;
      binding.addTime(const Duration(seconds: 10)); // or longer if needed
    await tester.pumpWidget(MyApp());

    await tester.enterText(find.byKey(Key('phoneInput')), 'test');
    await tester.enterText(find.byKey(Key('passwordInput')), 'test');
    await tester.tap(find.byIcon(Icons.lock));

    SharedPreferences prefs = await SharedPreferences.getInstance();
    expect(prefs.getString('phone'), 'test');
    expect(prefs.getString('password'), 'test');
  });