widget_test_stream_wtf.dart

  testWidgets('StreamController adding null wtf', (WidgetTester tester) async {
    final source = StreamController<String>();
    var index = 0;
    await tester.pumpWidget(MaterialApp(
      home: StreamBuilder(
        stream: source.stream,
        builder: (context, snapshot) {
          index += 1;
          return Text('$index');
        },
      ),
    ));
    expect(find.text('1'), findsOneWidget);

    source.add('Hello');
    await tester.pump();
    expect(find.text('2'), findsOneWidget);

    source.add('Bye');
    await tester.pump();
    expect(find.text('3'), findsOneWidget);

    source.close();
  });