[llvm-dev] [RFC] Cross-project lit test suite

[via llvm-dev]

> -----Original Message-----
> From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of David Greene
> via llvm-dev
> Sent: Wednesday, January 27, 2021 10:29 AM
> To: jh7370.2008 at my.bristol.ac.uk; llvm-dev <llvm-dev at lists.llvm.org>
> Subject: Re: [llvm-dev] [RFC] Cross-project lit test suite
> 
> James Henderson via llvm-dev <llvm-dev at lists.llvm.org> writes:
> 
> > Currently, there is no location where lit tests that use both clang and
> LLD
> > can be put, whilst the llvm-symbolizer cases I’ve hit are testing
> > llvm-symbolizer (and not LLD), so don’t really fit in the LLD test
> suite. I
> > therefore have prototyped a lit test suite that would be part of the
> > monorepo, and which can support tests that use elements from multiple
> > projects - see
> https://urldefense.com/v3/__https://reviews.llvm.org/D95339__;!!JmoZiZGBv3
> RvKRSx!vWidWrbKJid6-eIKVUT-dGDzcG-65TMZMzhyd33jgyBwi7p-JRSgFVZkxqKCvkqW4A$
> . Tests could be added to
> > this suite as needed. The suite is modelled as an additional top-level
> > directory, and is enabled by enabling the “cross-project-tests” project
> in
> > CMake.
> 
> This is fantastic!
> 
> > Back in October 2019, there was an extensive discussion on end-to-end
> > testing and how to write them (starting from
> > https://urldefense.com/v3/__https://lists.llvm.org/pipermail/cfe-
> dev/2019-October/063509.html__;!!JmoZiZGBv3RvKRSx!vWidWrbKJid6-eIKVUT-
> dGDzcG-65TMZMzhyd33jgyBwi7p-JRSgFVZkxqJU8k_M_Q$ ).
> > The suggestion was that these tests would be lit-based and run as part
> > of check-all, and would not be inside the clang tree, although there
> > was some opposition. This concluded with a round table. Unfortunately,
> > I am unaware of what the conclusion of that round table conversation
> > was, so it’s possible that what I am proposing is redundant/being
> > worked on by someone else.
> 
> I started that thread and IIRC we ended up with the suggestion that such
> tests should live in test-suite.  As you noted having tests separated
> from the monorepo is less than ideal.  I haven't done anything with this
> conclusion yet, mostly due to lack of time.  If your proposal gains
> traction I would like to see if we could build end-to-end testing on top
> of it.
> 
> > Additionally, I don’t consider all classes of tests that the proposed
> > lit suite would be useful for to be “end-to-end” testing.
> 
> Agreed.  There are various classes of tests that could make use of your
> proposed layout, one of which is "end-to-end."  Your proposal doesn't
> provide end-to-end testing per se, but it does make adding end-to-end
> tests later on more straightforward.
> 
>              -David

I think a useful distinction here is that lit tests are generally very
focused on a specific feature/function, where test-suite has a much
broader scope.  Another slice at it would be that lit tests tend to be
"regression" tests, while test-suite is more of an "integration" suite.

I am not a QA person so I may be abusing some of these terms, but that's
how I look at it.  Sometimes writing that focused lit test ends up
depending on multiple tools, and the cross-project lit suite would be a
good place to drop those; debuginfo-tests is a prime example.
--paulr