On 5/7/19 8:23 AM, shuah wrote: > On 5/7/19 2:01 AM, Greg KH wrote: >> On Mon, May 06, 2019 at 08:14:12PM -0700, Frank Rowand wrote: >>> On 5/1/19 4:01 PM, Brendan Higgins wrote: >>>> ## TLDR >>>> >>>> I rebased the last patchset on 5.1-rc7 in hopes that we can get this in >>>> 5.2. >>>> >>>> Shuah, I think you, Greg KH, and myself talked off thread, and we agreed >>>> we would merge through your tree when the time came? Am I remembering >>>> correctly? >>>> >>>> ## Background >>>> >>>> This patch set proposes KUnit, a lightweight unit testing and mocking >>>> framework for the Linux kernel. >>>> >>>> Unlike Autotest and kselftest, KUnit is a true unit testing framework; >>>> it does not require installing the kernel on a test machine or in a VM >>>> and does not require tests to be written in userspace running on a host >>>> kernel. Additionally, KUnit is fast: From invocation to completion KUnit >>>> can run several dozen tests in under a second. Currently, the entire >>>> KUnit test suite for KUnit runs in under a second from the initial >>>> invocation (build time excluded). >>>> >>>> KUnit is heavily inspired by JUnit, Python's unittest.mock, and >>>> Googletest/Googlemock for C++. KUnit provides facilities for defining >>>> unit test cases, grouping related test cases into test suites, providing >>>> common infrastructure for running tests, mocking, spying, and much more. >>> >>> As a result of the emails replying to this patch thread, I am now >>> starting to look at kselftest. My level of understanding is based >>> on some slide presentations, an LWN article, https://kselftest.wiki.kernel.org/ >>> and a _tiny_ bit of looking at kselftest code. >>> >>> tl;dr; I don't really understand kselftest yet. >>> >>> >>> (1) why KUnit exists >>> >>>> ## What's so special about unit testing? >>>> >>>> A unit test is supposed to test a single unit of code in isolation, >>>> hence the name. There should be no dependencies outside the control of >>>> the test; this means no external dependencies, which makes tests orders >>>> of magnitudes faster. Likewise, since there are no external dependencies, >>>> there are no hoops to jump through to run the tests. Additionally, this >>>> makes unit tests deterministic: a failing unit test always indicates a >>>> problem. Finally, because unit tests necessarily have finer granularity, >>>> they are able to test all code paths easily solving the classic problem >>>> of difficulty in exercising error handling code. >>> >>> (2) KUnit is not meant to replace kselftest >>> >>>> ## Is KUnit trying to replace other testing frameworks for the kernel? >>>> >>>> No. Most existing tests for the Linux kernel are end-to-end tests, which >>>> have their place. A well tested system has lots of unit tests, a >>>> reasonable number of integration tests, and some end-to-end tests. KUnit >>>> is just trying to address the unit test space which is currently not >>>> being addressed. >>> >>> My understanding is that the intent of KUnit is to avoid booting a kernel on >>> real hardware or in a virtual machine. That seems to be a matter of semantics >>> to me because isn't invoking a UML Linux just running the Linux kernel in >>> a different form of virtualization? >>> >>> So I do not understand why KUnit is an improvement over kselftest. > > They are in two different categories. Kselftest falls into black box > regression test suite which is a collection of user-space tests with a > few kernel test modules back-ending the tests in some cases. > > Kselftest can be used by both kernel developers and users and provides > a good way to regression test releases in test rings. > > KUnit is a white box category and is a better fit as unit test framework > for development and provides a in-kernel testing. I wouldn't view them > one replacing the other. They just provide coverage for different areas > of testing. I don't see what about kselftest or KUnit is inherently black box or white box. I would expect both frameworks to be used for either type of testing. > I wouldn't view KUnit as something that would be easily run in test rings for example. I don't see why not. -Frank > > Brendan, does that sound about right? > >>> >>> It seems to me that KUnit is just another piece of infrastructure that I >>> am going to have to be familiar with as a kernel developer. More overhead, >>> more information to stuff into my tiny little brain. >>> >>> I would guess that some developers will focus on just one of the two test >>> environments (and some will focus on both), splitting the development >>> resources instead of pooling them on a common infrastructure. > >>> What am I missing? >> >> kselftest provides no in-kernel framework for testing kernel code >> specifically. That should be what kunit provides, an "easy" way to >> write in-kernel tests for things. >> >> Brendan, did I get it right? > thanks, > -- Shuah > . >
