void () { myFixture.addClass("public class B { void main() {} }"); IdeaTestUtil.withLevel(getModule(), LanguageLevel.JDK_21_PREVIEW, () -> { myFixture.configureByText("MainTest.java", """ class A extends B {} """); List<GutterMark> marks = myFixture.findAllGutters(); assertEquals(1, marks.size()); }); }