### Question:
LegacyTaglibFunctions { public static String toUpperCase(@Nullable final String input) { if (input == null) { return ""; } return input.toUpperCase(Locale.ENGLISH); }  static String toUpperCase(@Nullable final String input); static String toLowerCase(@Nullable final String input); static int indexOf(@Nullable String input, @Nullable String substring); static boolean contains(@Nullable final String input, @Nullable final String substring); static boolean containsIgnoreCase(@Nullable String input, @Nullable String substring); static boolean startsWith(@Nullable String input, @Nullable String substring); static boolean endsWith(@Nullable String input, @Nullable String substring); static String substring(@Nullable String input, int beginIndex, int endIndex); static String substringAfter(@Nullable String input, @Nullable String substring); static String substringBefore(@Nullable String input, @Nullable String substring); static String trim(@Nullable final String input); static String replace(
            @Nullable String input,
            @Nullable String substringBefore,
            final String substringAfter); static String[] split(
            @Nullable String input,
            @Nullable String delimiters); static int length(@Nullable final Object obj); static String join(@Nullable final String[] array, @Nullable String separator);  }### Answer:
@Test public void testToUpperCase() { assertThat(toUpperCase(null)).isEqualTo(""); assertThat(toUpperCase("Foo")).isEqualTo("FOO"); }