flutter automatic testing : Tap on a button don't work in drawer

Question

I'm trying to do some TDD with flutter and when the test is running, tapping on a button doesn't work if it's in a drawer. The button works perfectly fine with a normal user.

In the following example we press on two buttons which print a message in the console. Here's the actions :
locate and tap on a button in the scaffold: OK
open the drawer: OK
Locate button in drawer: OK
Tap on the drawer button: nothing happen

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('Test that drawer is apparing and we can click on button',
  (WidgetTester tester) async {
final scaffoldKey = GlobalKey<ScaffoldState>();

await tester.pumpWidget(new MaterialApp(
  title: 'Where Assistant',
  home: Scaffold(
    key: scaffoldKey,
    body: Column(
      children: <Widget>[
        Text('test text'),
        RaisedButton(
          onPressed: () {
            print('OK on main screen');
          },
          child: Icon(Icons.access_alarm),
        ),
      ],
    ),
    drawer: Drawer(
      // Add a ListView to the drawer. This ensures the user can scroll
      // through the options in the Drawer if there isn't enough vertical
      // space to fit everything.
      child: ListView(
        // Important: Remove any padding from the ListView.
        padding: EdgeInsets.zero,
        children: <Widget>[
          DrawerHeader(
            child: Text('Drawer Header'),
            decoration: BoxDecoration(
              color: Colors.blue,
            ),
          ),
          ListTile(
            title: Text('Item 2'),
            onTap: () {
              // Update the state of the app
              // ...
            },
          ),
          RaisedButton(
            onPressed: () {
              print('OK drawer');
            },
            child: Icon(Icons.add),
          )
        ],
      ),
    ),
  ),
));

await tester.pump();

expect(find.text('test text'), findsOneWidget);
expect(find.byIcon(Icons.access_alarm), findsOneWidget);
await tester.tap(find.byIcon(Icons.access_alarm));
expect(find.byIcon(Icons.add), findsNothing);

scaffoldKey.currentState.openDrawer();
await tester.pump(); // drawer should appear

expect(find.text('Item 2'), findsOneWidget);
expect(find.byIcon(Icons.add), findsOneWidget);
await tester.tap(find.byIcon(Icons.add));
print('end of test');
  });
}

Answer 1

I also ran into a similar issue.

The tester was able to find the FlatButton in the drawer:

expect(find.byType(FlatButton), findsOneWidget);

tester.tap did not appear to be working:

await tester.tap(find.byType(FlatButton));

But the solution mentioned in this Flutter issue did work:

FlatButton button = find.widgetWithText(FlatButton, 'TextExample').evaluate().first.widget;
button.onPressed();