Add flutter_driver test.

Author: dvc94ch

Diff for: .github/workflows/ci.yml

@@ -99,6 +99,10 @@ jobs:
       if: matrix.platform.cross == false
       run: flutter test
 
+    - name: Flutter driver tests
+      if: matrix.platform.cross == false
+      run: cargo flutter --dart-main test_driver/app.dart --drive run
+
   lint:
     runs-on: ubuntu-latest
     steps:

Diff for: lib/main.dart

@@ -55,11 +55,13 @@ class _MyHomePageState extends State<MyHomePage> {
             Text(
               '$_counter',
               style: Theme.of(context).textTheme.display1,
+              key: Key('counter'),
             ),
           ],
         ),
       ),
       floatingActionButton: FloatingActionButton(
+        key: Key('increment'),
         onPressed: _incrementCounter,
         tooltip: 'Increment',
         child: Icon(Icons.add),