Re: ert.el --- Emacs Lisp Regression Testing

[Richard Stallman <rms@gnu.org>]

    For a general-purpose display testing, we need to add code to the
    display engine (both its high-level device-independent part, and
    lower-level display backend) that would expose to a Lisp application
    the glyphs that are produced by the display engine and the
    backend-dependent display commands sent to the display API
    (termcap/terminfo for text terminal, X for X Window system, etc.).

That sounds like a big job, and most of it for no purpose other than
testing.  I tend to doubt it would pay for itself in terms
of future effort saved.