Re: call for more ert tests

[Eli Zaretskii <eliz@gnu.org>]

> From: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
> Cc: Glenn Morris <rgm@gnu.org>
> Date: Tue, 25 Jun 2013 19:18:25 +0200
> 
> But a real test coverage would require tests for the rendered 
> layout.  Which would be hard to write and even worse probably breaking all the 
> time when rendering is improved and thus the output changes.

The fact that the "correct" results change with development is a fact
of life in every project, not just in Emacs.  It is detected very
simply, when the test fails.  Then you analyze the failure, understand
that the expected results are wrong, and modify them to follow suit.
Case closed.

> Therefore having a policy to demand tests for new features might be counter 
> productive.  On the other hand maintainers should at least ask for test cases 
> when they think a new feature could benefit from tests.  Which in my 
> experience, as somebody who is relatively new to contributing to Emacs, does 
> not seem to happen at all.

If you don't have good test coverage, you cannot regress-test, so you
can never be sure that a change you just made doesn't break something.
It's as simple as that, and I'm sure you know it.