Re: call for more ert tests

[Eli Zaretskii]

> From: Stefan Merten <address@hidden>
> Comments: In-reply-to Glenn Morris <address@hidden>
>       message dated "Mon, 24 Jun 2013 13:31:50 -0400."
> Date: Wed, 26 Jun 2013 11:22:24 +0200
> 
> May be I do not understand Lars' intentions here, but what is testing
> the C code good for at all? I mean there is an API - or rather: lots
> of APIs - and *this* is what needs testing. The C code to me looks
> like an implementation detail I'd not write tests for. Or at least
> separate those tests clearly from the API tests.

You seem to think that every C code in Emacs is part or a subroutine
of some Lisp API.  But that is false: e.g., the display engine is
implemented almost entirely in C.  If you have no test harness for
testing that, you cannot be sure, for example, that some change didn't
break cursor positioning (which happened a lot of time and will most
probably happen again, by a sheer coincidence -- or maybe due to
something else ;-).

Other important parts of Emacs that are implemented almost entirely in
C include:

  . GC

  . keyboard input

  . interaction with subprocesses

  . file I/O

There's probably more; these are just off the top of my head.