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

[Eli Zaretskii <eliz@gnu.org>]

> From: Richard Stallman <rms@gnu.org>
> CC: ohler+emacs@fastmail.net, emacs-devel@gnu.org
> Date: Sun, 06 Jan 2008 03:10:01 -0500
> 
>     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 don't see why it would be a big job.  Describing an iterator
structure and the glyph objects it produces is not hard, and neither
is the sequence of display API calls we issue to draw.

Anyway, if we ever want to have a regression testing suite for Emacs,
this job is hardly avoidable.  Without a good test suite, any
significant changes to core machinery runs a high risk of introducing
new and exciting bugs.