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Subject: Re: [RFC v2 00/14] kunit: introduce KUnit, the Linux kernel unit
 testing framework
To:     Brendan Higgins <brendanhiggins@google.com>,
        gregkh@linuxfoundation.org, keescook@google.com, mcgrof@kernel.org
Cc:     joel@jms.id.au, mpe@ellerman.id.au, joe@perches.com, brakmo@fb.com,
        rostedt@goodmis.org, Tim.Bird@sony.com, khilman@baylibre.com,
        julia.lawall@lip6.fr, linux-kselftest@vger.kernel.org,
        kunit-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        jdike@addtoit.com, richard@nod.at, linux-um@lists.infradead.org,
        daniel@ffwll.ch, dri-devel@lists.freedesktop.org, robh@kernel.org,
        dan.j.williams@intel.com, linux-nvdimm@lists.01.org,
        kieran.bingham@ideasonboard.com, Shuah Khan <shuah@kernel.org>
References: <20181023235750.103146-1-brendanhiggins@google.com>
From:   Shuah Khan <shuah@kernel.org>
Message-ID: <4b6eb273-8fe0-75be-dea0-fbbf17a7158c@kernel.org>
Date:   Thu, 25 Oct 2018 11:40:18 -0600
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On 10/23/2018 05:57 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/
> 
> ## Changes Since Last Version
> 
>  - Updated patchset to apply cleanly on 4.19.
>  - Stripped down patchset to focus on just the core features (I dropped
>    mocking, spying, and the MMIO stuff for now; you can find these
>    patches here: https://kunit-review.googlesource.com/c/linux/+/1132),
>    as suggested by Rob.
>  - Cleaned up some of the commit messages and tweaked commit order a
>    bit based on suggestions.
> 

I am a bit behind on reviewing this patch series.

Just a quick note that I will start looking at these early next week.

thanks,
-- Shuah