void () { OptPane pane1 = pane(checkbox("one", "One"), checkbox("two", "Two")); OptPane pane2 = pane(checkbox("three", "Three"), checkbox("four", "Four")); OptPane result = pane(tabs( pane1.asTab("Tab1"), pane2.asTab("Tab2") )); OptControl three = result.findControl("three"); assertTrue(three instanceof OptCheckbox checkbox && checkbox.label().label().equals("Three")); }