CategoryHelper { public static CategoryPath addSubCategory(CategoryPath categoryPath, String category) { List<String> categoryPathList = toList(categoryPath); categoryPathList.add(category); return toCategoryPath(categoryPathList); }  static CategoryPath addSubCategory(CategoryPath categoryPath, String category); static CategoryPath addParentCategory(String category, CategoryPath categoryPath);  }
@Test public void testAddSubCategory() { CategoryPath result = CategoryHelper.addSubCategory(new CategoryPath("a/b/c", '/'), "d"); assertEquals("a/b/c/d", result.toString()); }