TabPanelInfo panel = (TabPanelInfo) frame.getChildrenWidgets().get(0);
WidgetInfo button_1 = panel.getChildrenWidgets().get(0);
assertTrue(isVisible(button_1));
// do CREATE
WidgetInfo newButton = createButton();
panel.command_CREATE2(newButton, null);
assertEditor(
"public class Test implements EntryPoint {",
" public void onModuleLoad() {",
" RootPanel rootPanel = RootPanel.get();",
" {",