On Thu, Aug 27, 2020 at 9:14 PM Marco Elver elver@google.com wrote:
On Thu, Jul 02, 2020 at 12:14AM -0700, David Gow wrote:
As discussed in [1], KUnit tests have hitherto not had a particularly consistent naming scheme. This adds documentation outlining how tests and test suites should be named, including how those names should be used in Kconfig entries and filenames.
Signed-off-by: David Gow davidgow@google.com Reviewed-by: Kees Cook keescook@chromium.org
...
+An example Kconfig entry:
+.. code-block:: none
config FOO_KUNIT_TESTtristate "KUnit test for foo" if !KUNIT_ALL_TESTSdepends on KUNITdefault KUNIT_ALL_TESTShelpThis builds unit tests for foo.For more information on KUnit and unit tests in general, please referto the KUnit documentation in Documentation/dev-tools/kunitIf unsure, say N+Test Filenames +==============
+Where possible, test suites should be placed in a separate source file in the +same directory as the code being tested.
+This file should be named ``<suite>_kunit.c``. It may make sense to strip +excessive namespacing from the source filename (e.g., ``firmware_kunit.c`` instead of +``<drivername>_firmware.c``), but please ensure the module name does contain the +full suite name.
First of all, thanks for the talk yesterday! I only looked at this because somebody pasted the LKML link. :-)
No worries! Clearly this document needed linking -- even I was starting to suspect the reason no-one was complaining about this was that no-one had read it. :-)
The example about excessive namespacing seems confusing. Was it supposed to be
[...] firmware_kunit.c`` instead of ``<drivername>_firmware_kunit.c [...]?
Whoops, yes. I'll fix that.
While I guess this ship has sailed, and *_kunit.c is the naming convention now, I hope this is still just a recommendation and names of the form *-test.c are not banned!
The ship hasn't technically sailed until this patch is actually accepted. Thus far, we hadn't had any real complaints about the _kunit.c idea, though that may have been due to this email not reaching enough people. If you haven't read the discussion in https://lore.kernel.org/linux-kselftest/202006141005.BA19A9D3@keescook/t/#u it's worthwhile: the _kunit.c name is discussed, and Kees lays out some more detailed rationale for it as well.
$> git grep 'KUNIT.*-test.o' drivers/base/power/Makefile:obj-$(CONFIG_PM_QOS_KUNIT_TEST) += qos-test.o drivers/base/test/Makefile:obj-$(CONFIG_KUNIT_DRIVER_PE_TEST) += property-entry-test.o fs/ext4/Makefile:obj-$(CONFIG_EXT4_KUNIT_TESTS) += ext4-inode-test.o kernel/Makefile:obj-$(CONFIG_SYSCTL_KUNIT_TEST) += sysctl-test.o lib/Makefile:obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o lib/kunit/Makefile:obj-$(CONFIG_KUNIT_TEST) += kunit-test.o lib/kunit/Makefile:obj-$(CONFIG_KUNIT_TEST) += string-stream-test.o lib/kunit/Makefile:obj-$(CONFIG_KUNIT_EXAMPLE_TEST) += kunit-example-test.o
$> git grep 'KUNIT.*_kunit.o' # Returns nothing
This was definitely something we noted. Part of the goal of having _kunit.c as a filename suffix (and, perhaps more importantly, the _kunit module name suffix) was to have a way of both distinguishing KUnit tests from non-KUnit ones (of which there are quite a few already with -test names), and to have a way of quickly determining what modules contain KUnit tests. That really only works if everyone is using it, so the plan was to push this as much as possible. This'd probably include renaming most of the existing test files to match, which is a bit of a pain (particularly when converting non-KUnit tests to KUnit and similar), but is a one-time thing.
Just an idea: Maybe the names are also an opportunity to distinguish real _unit_ style tests and then the rarer integration-style tests. I personally prefer using the more generic *-test.c, at least for the integration-style tests I've been working on (KUnit is still incredibly valuable for integration-style tests, because otherwise I'd have to roll my own poor-man's version of KUnit, so thank you!). Using *_kunit.c for such tests is unintuitive, because the word "unit" hints at "unit tests" -- and having descriptive (and not misleading) filenames is still important. So I hope you won't mind if *-test.c are still used where appropriate.
As Brendan alluded to in the talk, the popularity of KUnit for these integration-style tests came as something of a surprise (more due to our lack of imagination than anything else, I suspect). It's great that it's working, though: I don't think anyone wants the world filled with more single-use test "frameworks" than is necessary!
I guess the interesting thing to note is that we've to date not really made a distinction between KUnit the framework and the suite of all KUnit tests. Maybe having a separate file/module naming scheme could be a way of making that distinction, though it'd really only appear when loading tests as modules -- there'd be no indication in e.g., suite names or test results. The more obvious solution to me (at least, based on the current proposal) would be to have "integration" or similar be part of the suite name (and hence the filename, so _integration_kunit.c or similar), though even I admit that that's much uglier. Maybe the idea of having the subsystem/suite distinction be represented in the code could pave the way to having different suites support different suffixes like that.
Do you know of any cases where something has/would have both unit-style tests and integration-style tests built with KUnit where the distinction needs to be clear?
Brendan, Kees: do you have any thoughts?
Thanks, -- Marco
Cheers, -- David