Re: unencodable-char-position [Re: Several serious problems]

[Richard Stallman]

    I implemented that and tried on several files.  But, it
    seems that such kind of feature is not that helpful.

    In the case that the buffer contains many unencodable chars,
    usually the specified coding system is wrong, and we must
    use a different coding system.  So, it is not that
    interesting to know where are the other unencodable
    characters.

    In the case that the buffer contains a few unencodable
    chars, as it's seldam that more than one of them appear in
    one window, highlighting the other unencodable chars is not
    that useful.

These seem like persuasive arguments; it sounds good.

How can I make a test case to observe it functioning?
I tried but I couldn't get encoding to "fail".