Feature request : Shortcut to create tests

Would be nice to have a shortcut to create test when we have one of those popup:

A bonus would be that if the class is a widget it create a template for widget test, if not unit test.

That a functionality we have already on Android:

It's very useful because it create a template test file directly in same place/package as the class.
For our case if we have a class in `lib/catalog/bloc/mybloc.dart` it will create a test file in `test/catalog/bloc/mybloc_test.dart`