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

[Todd Fiala]

>  then it's a high level test, not a low level test.

Totally.  I wouldn't expect us to be calling that a unit test.  That's why
I keep calling it a collaboration test (where multiple live components are
being tested together, either as part of setup or actually being tested).
Definitely doesn't qualify as a simple unit test.

> The answer might be simply that what I’m thinking of isn’t so much a
“unit test” as a fancier kind of assertion...

That's kinda how I was viewing it.

On Fri, Oct 3, 2014 at 11:33 AM, Sean Callanan <scallanan at apple.com> wrote:

> The answer might be simply that what I’m thinking of isn’t so much a “unit
> test” as a fancier kind of assertion – one that requires a significant
> amount of extra computation.
> Such an assertion might be enabled by a setting, and then run in situ
> whenever LLDB is in the right state.
> E.g., when we happen to be dematerializing an expression result, run a
> bunch of extra tests to make sure the variable is in the state we expect it
> to be in.
>
> Sean
>
> On Oct 3, 2014, at 11:28 AM, Todd Fiala <tfiala at google.com> wrote:
>
> But we're not talking about only one or only the other.
>
> I'm as much as possible going to only use gtests when I want to verify a
> class does what I want, typically doing it in isolation from everything
> else.
>
> If/when I need to deal with some real world lldb class configuration doing
> something complex, I might be interested in the python setup, gtest test
> case side.  Not entirely sure how we'd wire that all up but that's
> something we can investigate.
>
> 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
>>
>>
>
>
> --
> Todd Fiala | Software Engineer | tfiala at google.com
>
>
>


-- 
Todd Fiala | Software Engineer | tfiala at google.com
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