@Test
 public void testConvertToKnownLocale() throws Exception {
   assertEquals(Optional.of("en"), Languages.convertToKnownLocale("en"));
   assertEquals(Optional.of("en"), Languages.convertToKnownLocale("en_US"));
   assertEquals(Optional.of("de"), Languages.convertToKnownLocale("de_DE"));
   assertEquals(Optional.empty(), Languages.convertToKnownLocale("WHATEVER"));
 }
 @Test(expected = NullPointerException.class)
 public void testConvertToKnownLocaleNull() {
   Languages.convertToKnownLocale(null);
 }