Re: burden of maintainance

[Chad Brown <yandros@gmail.com>]

> On 02 Oct 2015, at 11:24, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Tassilo Horn <tsdh@gnu.org>
>> Cc: Przemysław Wojnowski <esperanto@cumego.com>,
>>  andreas.roehler@online.de,  emacs-devel@gnu.org
>> Date: Fri, 02 Oct 2015 19:18:08 +0200
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>>>> Can you give an example? Of course not everything can be tested, but
>>>> many things can.
>>> 
>>> We are mis-communicating again: I meant features which display
>>> something or involve interactive keyboard input.
>> 
>> Emacs is in a better position here than most other tools because it has
>> keyboard macros and can easily inspect the things it displays, e.g., the
>> text properties or overlays at point.
> 
> We may be mis-communicating here.  Because I cannot see how examining
> text properties or overlays can test whether their display on screen
> is correct.  What am I missing?  Can you show an example of what you
> had in mind?

I believe that Tassilo is talking about tests in the vein of “does the buffer report containing the expected characters, in the expected order, with the expected properties, etc”, rather than “are the expected pixels on the display the expected colors at the expected times”. Similarly, tools exist to automate testing with a synthetic mouse and keyboard.

I had some experience with this kind of testing a long while back (roughly, 1995-2000). There are tools that can be used to automate tests of GUIs, but they were (I think still are, but I’m not current) fairly deeply complicated - that is, they use their own fairly extensive language and idiom. It would take significant effort to learn these test harnesses, especially if one wanted to drive them from elisp (unless the SotA has changed more than I think - which is possible).

That said, we found that we could get quite a lot of benefit out of automated testing that basically ignored the gui. I suspect that emacs could see roughly the same - while there are issues that require testing the gui, there are also a great many that don’t. Looking over the recent archives for emacs-devel, it seems like a majority of topics would fall into this “can ignore the gui” category. This might be enough to get emacs started toward a more test-driven development model.

Hope that helps,
~Chad