"1234567890123456日本語7日本語890",
	}
	for _, str := range tests {
		got := exactly16Bytes(str)
		if len(got) != 16 {
			t.Errorf("exactly16Bytes(%q) is %q, length %d", str, got, len(got))
		}
		// Make sure it is full runes.
		for _, c := range got {
			if c == utf8.RuneError {
				t.Errorf("exactly16Bytes(%q) is %q, has partial rune", str, got)
			}
		}
	}