fix unittest_nfc16 and comment the unusual behavior of <U+1D161>. :-/

test/unittest_nfc16.cc

@@ -52,7 +52,8 @@ const std::vector<TestEntry> testValues =
 		{ u"a\u0305\u033c", false,  IsNFC::No  , u"a\u033c\u0305"}, // a + <U+0305> + <U+033C> (overline + seagull_below)
 		{ u"a\u033c\u0305",  true,  IsNFC::Yes , u"a\u033c\u0305"}, // a + <U+033C> + <U+0305> (seagull_below + overline)
 
-		{ u"\U0001D161", false, IsNFC::No, u"x" }, // MUSICAL SYMBOL SIXTEENTH NOTE
+		 // MUSICAL SYMBOL SIXTEENTH NOTE -> will be decomposed and not re-composed according to Unicode data, for whatever reason. :-/
+		{ u"\U0001D161", false, IsNFC::No, u"\U0001d15f\U0001d16f" },
 		{ u16string_view(nullo, 1), true, IsNFC::Yes, u16string_view(nullo, 1)  },  // Yeah, 1 NUL byte
 		{ u16string_view(nullo, 4), true, IsNFC::Yes, u16string_view(nullo, 4)  },  // Yeah, 4 NUL bytes