On Fri, Sep 30, 2022 at 6:33 AM Michał Winiarski <michal.winiarski@xxxxxxxxx> wrote: > > On Tue, Sep 27, 2022 at 07:12:06PM -0300, Maíra Canal wrote: > > The drm_test_dp_mst_sideband_msg_req_decode repeats the same test > > structure with different parameters. This could be better represented > > by parameterized tests, provided by KUnit. > > > > In order to convert the tests to parameterized tests, the test case for > > the client ID was changed: instead of using get_random_bytes to generate > > the client ID, the client ID is now hardcoded in the test case. > > Generally "random" usage is not incompatible with parameterized tests, we can > create parameterized tests that use random data. > The idea is to pass a function that generates the actual param (where we have a > pointer to function as one of the members in "params" struct). > > For example, see "random_dp_query_enc_client_id" usage here: > https://lore.kernel.org/dri-devel/20220117232259.180459-7-michal.winiarski@xxxxxxxxx/ > > In this case, we just compare data going in with data going out (and the data > itself is not transformed in any way), so it doesn't really matter for coverage > and we can hardcode. > > -Michał FWIW, while the uses of randomness in DRM tests so far haven't concerned me much, I think we'll eventually want to have some way of ensuring the inputs to tests are deterministic. My thoughts are that (at some point) we'll add a kunit_random() function or similar, which will use a pseudorandom number generator which can be set to a deterministic seed before each test case. That way, there'd be a way to reproduce an error easily if it occurred. (Of course, there'd be a way of setting different or random seeds to preserve the extra coverage you'd otherwise get.) I don't think this is something worth holding up or changing existing tests at the moment, but having tests behave deterministically is definitely desirable, so +1 to avoiding get_random_bytes() if it's not giving you any real benefit. We've also had a few requests in the past for being able to pass in a custom set of parameters from userspace, which opens up some other interesting possibilities, though it's not a priority at the moment. Cheers, -- David
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