On 5/7/19 1:01 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. >> >> 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. kselftest provides a mechanism for in-kernel tests via modules. For example, see: tools/testing/selftests/vm/run_vmtests invokes: tools/testing/selftests/vm/test_vmalloc.sh loads module: test_vmalloc (which is built from lib/test_vmalloc.c if CONFIG_TEST_VMALLOC) A very quick and dirty search (likely to miss some tests) finds modules: test_bitmap test_bpf test_firmware test_printf test_static_key_base test_static_keys test_user_copy test_vmalloc -Frank > > Brendan, did I get it right? > > thanks, > > greg k-h > . >
