[pytest-dev] Test discovery

[Rob McDonald]

Thanks Florian,

It took me a while to digest everything you brought up - and to get things
working.

However, it was just what I needed.  Thanks a bunch,

Rob


On Mon, Aug 3, 2020 at 2:20 AM Florian Bruhin <me at the-compiler.org> wrote:

> Hey Rob,
>
> On Sat, Aug 01, 2020 at 11:16:52PM -0700, Rob McDonald wrote:
> > According to Google, 'How does pytest discover tests' is an oft-asked
> > question.  However most of those questions actually want to know 'What
> > criteria does pytest use to discover tests'...
> >
> > I'm working on a program that needs to scan a directory structure for
> > Python code and then execute some of that code -- much like pytest does.
> > So, I'd like to know _how_ does pytest discover (and run) tests.
> >
> > I've searched around in the source for where this happens, but I haven't
> > had any luck.  Much appreciated if someone can point me to the relevant
> > bits of code?  Otherwise, any pointers on best practices and
> > functions/methods to use for this sort of thing are appreciated.
>
> Most of it happens in pytest's internal "python" plugin:
>
> https://github.com/pytest-dev/pytest/blob/master/src/_pytest/python.py
>
> For a simpler example how pytest's collection tree works, see:
>
> https://docs.pytest.org/en/latest/reference.html#collection-hooks
> https://docs.pytest.org/en/latest/example/nonpython.html
>
> Finally, you might be interested in Oliver Bestwalter's talk "Abridged
> metaprogramming classics - this episode: pytest":
>
> https://github.com/obestwalter/abridged-meta-programming-classics
>
> There, Oliver implements a small subset of pytest's "magic" from scratch.
>
> Note, however, that there are various utility functions available in the
> stdlib
> (inspect, importlib, pkgutils) which make those kinds of tasks easier, at
> least
> with Python 3.5+. However, both pytest and Oliver's talk avoid them
> (because of
> Python 2 support and because it was a fun limitation, respectively).
>
> For a more straightforward implementation, you can roughly:
>
> - Use pkgutil.walk_packages to find modules
> - Use importlib.import_module to import them
> - Use inspect.getmembers to get e.g. functions
>
> I do the first two in my own project here:
>
> https://github.com/qutebrowser/qutebrowser/blob/master/qutebrowser/extensions/loader.py
>
> Florian
>
> --
> me at the-compiler.org (Mail/XMPP) | https://www.qutebrowser.org
>        https://bruhin.software/ |
> https://github.com/sponsors/The-Compiler/
>        GPG: 916E B0C8 FD55 A072 | https://the-compiler.org/pubkey.asc
>              I love long mails! | https://email.is-not-s.ms/
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/pytest-dev/attachments/20200805/e468d791/attachment.html>