This serves as a demo of creating a testing interface using WidgetController
as a common ground for our different test needs.
test/perf_widget.dart is considered the new interface to address
flutter/flutter#61511
test/testOps.dart is how user should write the test for the new interface.
Itself can be used as a live test by running flutter test test/testOps.dart
or as a test app by flutter run test/testOps.dart.
e2e.dart shows if we want to use the test for e2e, to make compatible with
flutter driver or other platform.
widget_test.dart is how user should use the test as unit test.