path: root/community/gsoc/project_ideas/testing_framework/discussion.mdwn
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authorThomas Schwinge <>2011-03-26 01:42:25 +0100
committerThomas Schwinge <>2011-03-26 01:42:25 +0100
commita2a4176bcd74dc6c607d48131f26cb5fa4affb3d (patch)
tree53a42a9eaa197a32edc1e2065feb1402179897ba /community/gsoc/project_ideas/testing_framework/discussion.mdwn
parent48d63562b1eb3e1211fe2ad803a3df704f9c342c (diff)
open_issues/unit_testing: Move discussion to community/gsoc/project_ideas/testing_framework/discussion.
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+freenode, #hurd channel, 2011-03-05:
+ <nixness> what about testing though?
+ <nixness> like sort of "what's missing? lets write tests for it so that
+ when someone gets to implementing it, he knows what to do. Repeat"
+ project
+ <antrik> you mean creating an automated testing framework?
+ <antrik> this is actually a task I want to add for this year, if I get
+ around to it :-)
+ <nixness> yeah I'd very much want to apply for that one
+ <nixness> cuz I've never done Kernel hacking before, but I know that with
+ the right tasks like "test VM functionality", I would be able to write up
+ the automated tests and hopefully learn more about what breaks/makes the
+ kernel
+ <nixness> (and it would make implementing the feature much less hand-wavy
+ and more correct)
+ <nixness> antrik, I believe the framework(CUnit right?) exists, but we just
+ need to write the tests.
+ <antrik> do you have prior experience implementing automated tests?
+ <nixness> lots of tests!
+ <nixness> yes, in Java mostly, but I've played around with CUnit
+ <antrik> ah, great :-)
+ <nixness> here's what I know from experience: 1) write basic tests. 2)
+ write ones that test multiple features 3) stress test [option 4)
+ benchmark and record to DB]
+ <youpi> well, what we'd rather need is to fix the issues we already know
+ from the existing testsuites :)
+[[GSoC project propsal|community/gsoc/project_ideas/testsuites]].
+ <nixness> youpi, true, and I think I should check what's available in way
+ of tests, but if the tests are "all or nothing" then it becomes really
+ hard to fix your mistakes
+ <youpi> they're not all or nothing
+ <antrik> youpi: the existing testsuites don't test specific system features
+ <youpi> libc ones do
+ <youpi> we could also check posixtestsuite which does too
+ <antrik> AFAIK libc has very few failing tests
+ <youpi> err, like twenty?
+ <youpi> € grep -v '^#' expected-results-i486-gnu-libc | wc -l
+ <youpi> 67
+ <youpi> nope, even more
+ <antrik> oh, sorry, I confused it with coreutils
+ <pinotree> plus the binutils ones, i guess
+ <youpi> yes
+ <antrik> anyways, I don't think relying on external testsuites for
+ regression testing is a good plan
+ <antrik> also, that doesn't cover unit testing at all
+ <youpi> why ?
+ <youpi> sure there can be unit testing at the translator etc. level
+ <antrik> if we want to implement test-driven development, and/or do serious
+ refactoring without too much risk, we need a test harness where we can
+ add specific tests as needed
+ <youpi> but more than often, the issues are at the libc / etc. level
+ because of a combination o fthings at the translator level, which unit
+ testing won't find out
+ * nixness yewzzz!
+ <nixness> sure unit testing can find them out. if they're good "unit" tests
+ <youpi> the problem is that you don't necessarily know what "good" means
+ <youpi> e.g. for posix correctness
+ <youpi> since it's not posix
+ <nixness> but if they're composite clever tests, then you lose that
+ granularity
+ <nixness> youpi, is that a blackbox test intended to be run at the very end
+ to check if you're posix compliant?
+ <antrik> also, if we have our own test harness, we can run tests
+ automatically as part of the build process, which is a great plus IMHO
+ <youpi> nixness: "that" = ?
+ <nixness> oh nvm, I thought there was a test stuie called "posix
+ correctness"
+ <youpi> there's the posixtestsuite yes
+ <youpi> it's an external one however
+ <youpi> antrik: being external doesn't mean we can't invoke it
+ automatically as part of the build process when it's available
+ <nixness> youpi, but being internal means it can test the inner workings of
+ certain modules that you are unsure of, and not just the interface
+ <youpi> sure, that's why I said it'd be useful too
+ <youpi> but as I said too, most bugs I've seen were not easy to find out at
+ the unit level
+ <youpi> but rather at the libc level
+ <antrik> of course we can integrate external tests if they exist and are
+ suitable. but that that doesn't preclude adding our own ones too. in
+ either case, that integration work has to be done too
+ <youpi> again, I've never said I was against internal testsuite
+ <antrik> also, the major purpose of a test suite is checking known
+ behaviour. a low-level test won't directly point to a POSIX violation;
+ but it will catch any changes in behaviour that would lead to one
+ <youpi> what I said is that it will be hard to write them tight enough to
+ find bugs
+ <youpi> again, the problem is knowing what will lead to a POSIX violation
+ <youpi> it's long work
+ <youpi> while libc / posixtestsuite / etc. already do that
+ <antrik> *any* unexpected change in behaviour is likely to cause bugs
+ somewher
+ <youpi> but WHAT is "expected" ?
+ <youpi> THAT is the issue
+ <youpi> and libc/posixtessuite do know that
+ <youpi> at the translator level we don't really
+ <youpi> see the recent post about link()
+[link(dir,name) should fail with
+ <youpi> in my memory jkoenig pointed it out for a lot of such calls
+ <youpi> and that issue is clearly not known at the translator level
+ <nixness> so you're saying that the tests have to be really really
+ low-level, and work our way up?
+ <youpi> I'm saying that the translator level tests will be difficult to
+ write
+ <antrik> why isn't it known at the translator level? if it's a translator
+ (not libc) bug, than obviously the translator must return something wrong
+ at some point, and that's something we can check
+ <youpi> because you'll have to know all the details of the combinations
+ used in libc, to know whether they'll lead to posix issues
+ <youpi> antrik: sure, but how did we detect that that was unexpected
+ behavior?
+ <youpi> because of a glib test
+ <youpi> at the translator level we didn't know it was an unexpected
+ behavior
+ <antrik> gnulib actually
+ <youpi> and if you had asked me, I wouldn't have known
+ <antrik> again, we do *not* write a test suite to find existing bugs
+ <youpi> right, took one for the other
+ <youpi> doesn't really matter actually
+ <youpi> antrik: ok, I don't care then
+ <antrik> we write a test suite to prevent future bugs, or track status of
+ known bugs
+ <youpi> (don't care *enough* for now, I mean)
+ <nixness> hmm, so write something up antrik for GSoC :) and I'll be sure to
+ apply
+ <antrik> now that we know some translators return a wrong error status in a
+ particular situation, we can write a test that checks exactly this error
+ status. that way we know when it is fixed, and also when it breaks again
+ <antrik> nixness: great :-)
+ <nixness> sweet. that kind of thing would also need a db backend
+ <antrik> nixness: BTW, if you have a good idea, you can send an application
+ for it even if it's not listed among the proposed tasks...
+ <antrik> so you don't strictly need a writeup from me to apply for this :-)
+ <nixness> antrik, I'll keep that in mind, but I'll also be checking your
+ draft page
+ <nixness> oh cool :)
+ <antrik> (and it's a well known fact that those projects which students
+ proposed themselfs tend to be the most successful ones :-) )
+ * nixness draft initiated
+ <antrik> youpi: BTW, I'm surprised that you didn't mention libc testsuite
+ before... working up from there is probably a more effective plan than
+ starting with high-level test suites like Python etc...
+ <youpi> wasn't it already in the gsoc proposal?
+ <youpi> bummer
+ <antrik> nope
+freenode, #hurd channel, 2011-03-06:
+ <nixness> how's the hurd coding workflow, typically?
+*nixness* -> *foocraft*.
+ <foocraft> we're discussing how TDD can work with Hurd (or general kernel
+ development) on #osdev
+ <foocraft> so what I wanted to know, since I haven't dealt much with GNU
+ Hurd, is how do you guys go about coding, in this case
+ <tschwinge> Our current workflow scheme is... well... is...
+ <tschwinge> Someone wants to work on something, or spots a bug, then works
+ on it, submits a patch, and 0 to 10 years later it is applied.
+ <tschwinge> Roughly.
+ <foocraft> hmm so there's no indicator of whether things broke with that
+ patch
+ <foocraft> and how low do you think we can get with tests? A friend of mine
+ was telling me that with kernel dev, you really don't know whether, for
+ instance, the stack even exists, and a lot of things that I, as a
+ programmer, can assume while writing code break when it comes to writing
+ kernel code
+ <foocraft> Autotest seems promising
+See autotest link given above.
+ <foocraft> but in any case, coming up with the testing framework that
+ doesn't break when the OS itself breaks is hard, it seems
+ <foocraft> not sure if autotest isolates the mistakes in the os from
+ finding their way in the validity of the tests themselves
+ <youpi> it could be interesting to have scripts that automatically start a
+ sub-hurd to do the tests
+ <tschwinge> foocraft: To answer one of your earlier questions: you can do
+ really low-level testing. Like testing Mach's message passing. A
+ million times. The questions is whether that makes sense. And / or if
+ it makes sense to do that as part of a unit testing framework. Or rather
+ do such things manually once you suspect an error somewhere.
+ <tschwinge> The reason for the latter may be that Mach IPC is already
+ heavily tested during normal system operation.
+ <tschwinge> And yet, there still may be (there are, surely) bugs.
+ <tschwinge> But I guess that you have to stop at some (arbitrary?) level.
+ <foocraft> so we'd assume it works, and test from there
+ <tschwinge> Otherwise you'd be implementing the exact counter-part of what
+ you're testing.
+ <tschwinge> Which may be what you want, or may be not. Or it may just not
+ be feasible.
+ <foocraft> maybe the testing framework should have dependencies
+ <foocraft> which we can automate using make, and phony targets that run
+ tests
+ <foocraft> so everyone writes a test suite and says that it depends on A
+ and B working correctly
+ <foocraft> then it'd go try to run the tests for A etc.
+ <tschwinge> Hmm, isn't that -- on a high level -- have you have by
+ different packages? For example, the perl testsuite depends (inherently)
+ on glibc working properly. A perl program's testsuite depends on perl
+ working properly.
+ <foocraft> yeah, but afaik, the ordering is done by hand
+freenode, #hurd channel, 2011-03-07:
+ <antrik> actually, I think for most tests it would be better not to use a
+ subhurd... that leads precisely to the problem that if something is
+ broken, you might have a hard time running the tests at all :-)
+ <antrik> foocraft: most of the Hurd code isn't really low-level. you can
+ use normal debugging and testing methods
+ <antrik> gnumach of course *does* have some low-level stuff, so if you add
+ unit tests to gnumach too, you might run into issues :-)
+ <antrik> tschwinge: I think testing IPC is a good thing. as I already said,
+ automated testing is *not* to discover existing but unknown bugs, but to
+ prevent new ones creeping in, and tracking progress on known bugs
+ <antrik> tschwinge: I think you are confusing unit testing and regression
+ testing.
+ talks about unit testing, but a lot (most?) of it is actually about
+ regression tests...
+ <tschwinge> antrik: That may certainly be -- I'm not at all an expert in
+ this, and just generally though that some sort of automated testing is
+ needed, and thus started collecting ideas.
+ <tschwinge> antrik: You're of course invited to fix that.
+IRC, freenode, #hurd, 2011-03-08
+(After discussing the [[open_issues/anatomy_of_a_hurd_system]].)
+ <antrik> so that's what your question is actually about?
+ <foocraft> so what I would imagine is a set of only-this-server tests for
+ each server, and then we can have fun adding composite tests
+ <foocraft> thus making debugging the composite scenarios a bit less tricky
+ <antrik> indeed
+ <foocraft> and if you were trying to pass a composite test, it would also
+ help knowing that you still didn't break the server-only test
+ <antrik> there are so many different things that can be tested... the
+ summer will only suffice to dip into this really :-)
+ <foocraft> yeah, I'm designing my proposal to focus on 1) make/use a
+ testing framework that fits the Hurd case very well 2) write some tests
+ and docs on how to write good tests
+ <antrik> well, doesn't have to be *one* framework... unit testing and
+ regression testing are quite different things, which can be covered by
+ different frameworks