bug#22471: ert batch should print compile parsable error messages

[Phillip Lord]

Glenn Morris <rgm@gnu.org> writes:

> Why would you call the batch version of ert from within Emacs,
> when M-x ert exists and does colour, hyperlinking to source, etc?

M-x ert is nice, but has one main failure. It's not running in a clean,
controllable Emacs; it's running in my Emacs. I use M-x ert only when I
am debugging failing tests.

The rest of the time, I run tests in a clean, newly launched Emacs with
a sandboxed .emacs.d/elpa. As a secondary advantage, it can be easier to
test two or three Emacs versions at the same time.

I've been writing a library to help get around this problem, but
fundamentally, the only clean way to test code is not to run it in the
same Emacs as is launching it. At some point, I'd like to add the
ability to launch an emacs for every test.

Phil