[lldb-dev] unit testing C++ code in LLDB

[Zachary Turner]

If that's the case, I would argue that maybe the code needs to be written
to be more easily testable.  If you can't test a class without writing a
ton of setup code first, then it's a high level test, not a low level test.


It's hard to talk in the abstract though, maybe a concrete example would
help, so we can see the code being tested, and the setup required.

On Fri, Oct 3, 2014 at 11:26 AM, Todd Fiala <tfiala at google.com> wrote:

> > Why not just make it a python test?
>
> I think I see the usefulness for it.  You really want to test a C++ class
> at a low level and make sure it's working right.  But the state machine
> needed to feed it inputs and outputs is complex enough that it would take a
> lot of code to set that up right.  And you want it to always reflect what
> lldb is doing, not some non-real-world static test environment where it can
> get out of sync with the real lldb code.
>
> -Todd
>
> On Fri, Oct 3, 2014 at 11:24 AM, Zachary Turner <zturner at google.com>
> wrote:
>
>> I think it diminishes their usefulness if they're only available to
>> people willing to run them a specific way.  The python support on Windows
>> isn't as rosy as it is on other platforms, and it's still very difficult to
>> build LLDB with python support on Windows.  I might be the only person
>> doing it.  I'm trying to improve it, but I don't see it being in the same
>> place as it is on other platforms for a while.
>>
>> Even ignoring that though, I think if your test needs to do setup in
>> python, it should just be a regular python test of the public API like
>> everything else.  Regardless, the functionality available to you from C++
>> is a superset of that available to you from python.  You can even use the
>> actual public API from C++, which is the same as what you'd be doing in
>> python.  If you actually need to piggyback off of lots of already-written
>> python code, then I'm wondering why this particular test is better suited
>> for a gtest.  Why not just make it a python test?
>>
>> On Fri, Oct 3, 2014 at 11:01 AM, Sean Callanan <scallanan at apple.com>
>> wrote:
>>
>>> Zach,
>>>
>>> I can live with two entry points – one without the Python dependency,
>>> one accessible through Python.  As you (and Greg, in the past) suggest, we
>>> can have a special public API for running unit tests – probably only in
>>> debug builds – and use that API from Python.
>>>
>>> I’m not sure that all internal unit tests should do their setup in C++.
>>> I think it makes the test more fragile – and wastes a lot of the machinery
>>> we already have – to write a bunch of process-control logic in C++ when
>>> what I actually want to test is something specific in an unrelated class.
>>> LLDB is pretty closely tied to Python – for the test cases I write for the
>>> expression parser, I think I’d be willing to mandate that Python be
>>> available rather than make setup more challenging.
>>>
>>> So that both use cases can coexist, we can just make sure that both the
>>> gtest runner and the SB API have the ability to run a subset of the unit
>>> tests; the gtest runner runs all those that don’t require external setup,
>>> and the SB API can select the tests that need to run with a specific
>>> initial setup.
>>>
>>> Is that something that gtest would support?
>>>
>>> Sean
>>>
>>> On Oct 3, 2014, at 10:37 AM, Zachary Turner <zturner at google.com> wrote:
>>>
>>> I don't think the unit tests should depend on the python tests.  They
>>> should be self contained.  In other words, the unit tests must be useful to
>>> someone who is compiling without support for embedded python.  I wouldn't
>>> want to have a unit test which is only useful if it's called from Python
>>> which has already done some initial setup.  Still, if you want to avoid
>>> having another entry poitn for convenience, you could expose something from
>>> the public API that allows you to just say "run all the unittests".  But
>>> there shouldn't be any setup in the python.  All the setup necessary to run
>>> a given test should happen in C++.
>>>
>>> On Fri, Oct 3, 2014 at 10:23 AM, Sean Callanan <scallanan at apple.com>
>>> wrote:
>>>
>>>>
>>>> > On Oct 2, 2014, at 9:27 PM, Todd Fiala <tfiala at google.com> wrote:
>>>> >
>>>> > Hey Sean!
>>>> > …
>>>>
>>>> Thanks for the introduction!  It looks like this is definitely in the
>>>> direction of what I want.
>>>>
>>>> > If we want to do collaboration tests (integration tests, etc.), we're
>>>> probably into the "should be in python category", but we might have a few
>>>> low-level multi-class testing scenarios where we might want a different
>>>> gtest/functional, gtest/integration or something similar directory
>>>> structure to handle those.  Would be good to have discussion around that if
>>>> we find a valid use for it.
>>>>
>>>> One thing I would like to be able to do for the expression parser is
>>>> unit test in the context of a stopped process.
>>>> I’m thinking of scenarios where I’d like to test e.g. the
>>>> Materializer’s ability to read in variable data and make correct
>>>> ValueObjects.
>>>>
>>>> One way to achieve this that comes to mind is to have a hook into the
>>>> unit tests from the Python test suite, so we can set up the program’s state
>>>> appropriately using our normal Python apparatus and then exercise exactly
>>>> the functionality we want.
>>>>
>>>> Once we’ve got that kind of hook, we could just run all unit tests
>>>> right from the Python test suite and avoid having another entry point.
>>>>
>>>> If you want IDE-friendly output, you could have an IDE-level target
>>>> that runs test/dotest.py but singles out the unit tests.
>>>>
>>>> What do you think?
>>>>
>>>> Sean
>>>>
>>>
>>>
>>>
>>
>
>
> --
> Todd Fiala | Software Engineer | tfiala at google.com
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20141003/9c7942b9/attachment.html>