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? -Frank > > ## More information on KUnit > > There is a bunch of documentation near the end of this patch set that > describes how to use KUnit and best practices for writing unit tests. > For convenience I am hosting the compiled docs here: > https://google.github.io/kunit-docs/third_party/kernel/docs/ > Additionally for convenience, I have applied these patches to a branch: > https://kunit.googlesource.com/linux/+/kunit/rfc/v5.1-rc7/v1 > The repo may be cloned with: > git clone https://kunit.googlesource.com/linux > This patchset is on the kunit/rfc/v5.1-rc7/v1 branch. > > ## Changes Since Last Version > > None. I just rebased the last patchset on v5.1-rc7. >
