On 2/14/19 1:37 PM, Brendan Higgins wrote: > 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. > > ## 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. > > ## 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. > > ## 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/5.0-rc5/v4 > The repo may be cloned with: > git clone https://kunit.googlesource.com/linux > This patchset is on the kunit/rfc/5.0-rc5/v4 branch. > > ## Changes Since Last Version > > - Got KUnit working on (hypothetically) all architectures (tested on > x86), as per Rob's (and other's) request > - Punting all KUnit features/patches depending on UML for now. > - Broke out UML specific support into arch/um/* as per "[RFC v3 01/19] > kunit: test: add KUnit test runner core", as requested by Luis. > - Added support to kunit_tool to allow it to build kernels in external > directories, as suggested by Kieran. > - Added a UML defconfig, and a config fragment for KUnit as suggested > by Kieran and Luis. > - Cleaned up, and reformatted a bunch of stuff. > I have not read through the patches in any detail. I have read some of the code to try to understand the patches to the devicetree unit tests. So that may limit how valid my comments below are. I found the code difficult to read in places where it should have been much simpler to read. Structuring the code in a pseudo object oriented style meant that everywhere in a code path that I encountered a dynamic function call, I had to go find where that dynamic function call was initialized (and being the cautious person that I am, verify that no where else was the value of that dynamic function call). With primitive vi and tags, that search would have instead just been a simple key press (or at worst a few keys) if hard coded function calls were done instead of dynamic function calls. In the code paths that I looked at, I did not see any case of a dynamic function being anything other than the value it was originally initialized as. There may be such cases, I did not read the entire patch set. There may also be cases envisioned in the architects mind of how this flexibility may be of future value. Dunno. -Frank
