void () { TreeTest.test(TreeUtilVisitTest::rootDeep, test -> test.assertTree("+Root\n", () -> TreeUtil.expand(test.getTree(), 2, () -> test.assertTree(""" -Root -1 +11 +12 +13 -2 +21 +22 +23 -3 +31 +32 +33 """, test::done)))); }