MaterialDesignIcons { @NotNull @VisibleForTesting static Collection<String> getCategoriesFromFile(@NotNull File file) { String[] array = file.list(); if (array == null) { return Collections.emptyList(); } List<String> list = Arrays.asList(array); list.sort(String::compareTo); return list; } private  MaterialDesignIcons(); @Nullable static String getPathForBasename(@NotNull String basename); @NotNull static Collection<String> getCategories(); @NotNull static List<String> getIconNames(@NotNull String categoryName); @NotNull static URL getIcon(@NotNull String iconName, @NotNull String categoryName); @NotNull static URL getDefaultIcon();  }
@Test public void getCategoriesFromFile() { Object actual = MaterialDesignIcons.getCategoriesFromFile(Mockito.mock(File.class)); assertEquals(Collections.emptyList(), actual); }