Re: [PATCH v5] lib: add basic KUnit test for lib/math

From: Daniel Latypov
Date: Fri Apr 16 2021 - 14:10:42 EST

On Tue, Apr 13, 2021 at 5:33 PM Daniel Latypov <dlatypov@xxxxxxxxxx> wrote:
>
> On Mon, Apr 12, 2021 at 11:41 PM David Gow <davidgow@xxxxxxxxxx> wrote:
> >
> > On Tue, Apr 13, 2021 at 3:07 AM Daniel Latypov <dlatypov@xxxxxxxxxx> wrote:
> > >
> > > Add basic test coverage for files that don't require any config options:
> > > * part of math.h (what seem to be the most commonly used macros)
> > > * gcd.c
> > > * lcm.c
> > > * int_sqrt.c
> > > * reciprocal_div.c
> > > (Ignored int_pow.c since it's a simple textbook algorithm.)
> > >
> > > These tests aren't particularly interesting, but they
> > > * provide short and simple examples of parameterized tests
> > > * provide a place to add tests for any new files in this dir
> > > * are written so adding new test cases to cover edge cases should be easy
> > > * looking at code coverage, we hit all the branches in the .c files
> > >
> > > Signed-off-by: Daniel Latypov <dlatypov@xxxxxxxxxx>
> >
> > This looks good to me. A few comments/observations below, but nothing
> > that I think should actually block this.
> >
> > Reviewed-by: David Gow <davidgow@xxxxxxxxxx>
> >
> > -- David
> >
> > > ---
> > > Changes since v4:
> > > * add in test cases for some math.h macros (abs, round_up/round_down,
> > > div_round_down/closest)
> > > * use parameterized testing less to keep things terser
> > >
> > > Changes since v3:
> > > * fix `checkpatch.pl --strict` warnings
> > > * add test cases for gcd(0,0) and lcm(0,0)
> > > * minor: don't test both gcd(a,b) and gcd(b,a) when a == b
> > >
> > > Changes since v2: mv math_test.c => math_kunit.c
> > >
> > > Changes since v1:
> > > * Rebase and rewrite to use the new parameterized testing support.
> > > * misc: fix overflow in literal and inline int_sqrt format string.
> > > * related: commit 1f0e943df68a ("Documentation: kunit: provide guidance
> > > for testing many inputs") was merged explaining the patterns shown here.
> > > * there's an in-flight patch to update it for parameterized testing.
> > >
> > > v1: https://lore.kernel.org/lkml/20201019224556.3536790-1-dlatypov@xxxxxxxxxx/
> > > ---
> > > lib/math/Kconfig | 5 +
> > > lib/math/Makefile | 2 +
> > > lib/math/math_kunit.c | 264 ++++++++++++++++++++++++++++++++++++++++++
> > > 3 files changed, 271 insertions(+)
> > > create mode 100644 lib/math/math_kunit.c
> > >
> > > diff --git a/lib/math/Kconfig b/lib/math/Kconfig
> > > index f19bc9734fa7..6ba8680439c1 100644
> > > --- a/lib/math/Kconfig
> > > +++ b/lib/math/Kconfig
> > > @@ -15,3 +15,8 @@ config PRIME_NUMBERS
> > >
> > > config RATIONAL
> > > bool
> > > +
> > > +config MATH_KUNIT_TEST
> > > + tristate "KUnit test for lib/math" if !KUNIT_ALL_TESTS
> > > + default KUNIT_ALL_TESTS
> > > + depends on KUNIT
> >
> > This could have a description of the test and KUnit here, as mentioned
> > in the style guide doc:
> > https://www.kernel.org/doc/html/latest/dev-tools/kunit/style.html#test-kconfig-entries
> >
> > (I think it's sufficiently self explanatory that it's not essential,
> > but it could be nice to have a more detailed description of the things
> > being tested than just "lib/math".)
> >
>
> Done. I've left off the details about what the test tests so we have
> less places to go and update if/when new tests are added.
>
> > > diff --git a/lib/math/Makefile b/lib/math/Makefile
> > > index be6909e943bd..30abb7a8d564 100644
> > > --- a/lib/math/Makefile
> > > +++ b/lib/math/Makefile
> > > @@ -4,3 +4,5 @@ obj-y += div64.o gcd.o lcm.o int_pow.o int_sqrt.o reciprocal_div.o
> > > obj-$(CONFIG_CORDIC) += cordic.o
> > > obj-$(CONFIG_PRIME_NUMBERS) += prime_numbers.o
> > > obj-$(CONFIG_RATIONAL) += rational.o
> > > +
> > > +obj-$(CONFIG_MATH_KUNIT_TEST) += math_kunit.o
> > > diff --git a/lib/math/math_kunit.c b/lib/math/math_kunit.c
> > > new file mode 100644
> > > index 000000000000..80a087a32884
> > > --- /dev/null
> > > +++ b/lib/math/math_kunit.c
> > > @@ -0,0 +1,264 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Simple KUnit suite for math helper funcs that are always enabled.
> > > + *
> > > + * Copyright (C) 2020, Google LLC.
> > > + * Author: Daniel Latypov <dlatypov@xxxxxxxxxx>
> > > + */
> > > +
> > > +#include <kunit/test.h>
> > > +#include <linux/gcd.h>
> > > +#include <linux/kernel.h>
> > > +#include <linux/lcm.h>
> > > +#include <linux/reciprocal_div.h>
> > > +
> > > +static void abs_test(struct kunit *test)
> > > +{
> >
> > There's something weird about taking the absolute values of char
> > literals. I'm not sure if it's better to case integer literals (like
> > with 'short' below), or keep it as-is.
>
> I just thought it was amusing :)
> Converting it to be like the short test below.
>
> > > + KUNIT_EXPECT_EQ(test, abs('\0'), '\0');
> > > + KUNIT_EXPECT_EQ(test, abs('a'), 'a');
> > > + KUNIT_EXPECT_EQ(test, abs(-'a'), 'a');
> > > +
> > > + /* The expression in the macro is actually promoted to an int. */
> > > + KUNIT_EXPECT_EQ(test, abs((short)0), 0);
> > > + KUNIT_EXPECT_EQ(test, abs((short)42), 42);
> > > + KUNIT_EXPECT_EQ(test, abs((short)-42), 42);
> > > +
> > > + KUNIT_EXPECT_EQ(test, abs(0), 0);
> > > + KUNIT_EXPECT_EQ(test, abs(42), 42);
> > > + KUNIT_EXPECT_EQ(test, abs(-42), 42);
> > > +
> > > + KUNIT_EXPECT_EQ(test, abs(0L), 0L);
> > > + KUNIT_EXPECT_EQ(test, abs(42L), 42L);
> > > + KUNIT_EXPECT_EQ(test, abs(-42L), 42L);
> > > +
> > > + KUNIT_EXPECT_EQ(test, abs(0LL), 0LL);
> > > + KUNIT_EXPECT_EQ(test, abs(42LL), 42LL);
> > > + KUNIT_EXPECT_EQ(test, abs(-42LL), 42LL);
> > > +
> > > + /* Unsigned types get casted to signed. */
> > > + KUNIT_EXPECT_EQ(test, abs(0ULL), 0LL);
> > > + KUNIT_EXPECT_EQ(test, abs(42ULL), 42LL);
> >
> > A part of me is curious what the result is for -0x80000000, but I
> > guess that's not defined, so shouldn't be tested. :-)
>
> abs(-42ULL) == 42, but the compiler spits out a warning.
>
> > > +}
> > > +
> > > +static void int_sqrt_test(struct kunit *test)
> > > +{
> > > + KUNIT_EXPECT_EQ(test, int_sqrt(0UL), 0UL);
> > > + KUNIT_EXPECT_EQ(test, int_sqrt(1UL), 1UL);
> > > + KUNIT_EXPECT_EQ(test, int_sqrt(4UL), 2UL);
> > > + KUNIT_EXPECT_EQ(test, int_sqrt(5UL), 2UL);
> > > + KUNIT_EXPECT_EQ(test, int_sqrt(8UL), 2UL);
> > > + KUNIT_EXPECT_EQ(test, int_sqrt(1UL << 30), 1UL << 15);
> > > +}
> > > +
> >
> > _Maybe_ it's worth a comment here that round_up (and round_down) only
> > support rounding to powers of two?
> > (Either that, or also test roundup/rounddown to provide the contrast.)
>
> Adding in those test cases for v6.
> Andy had asked for those as well but I had forgotten them by the time
> I sent out v5.
>
> >
> > > +static void round_up_test(struct kunit *test)
> > > +{
> > > + KUNIT_EXPECT_EQ(test, round_up(0, 1), 0);
> > > + KUNIT_EXPECT_EQ(test, round_up(1, 2), 2);
> > > + KUNIT_EXPECT_EQ(test, round_up(3, 2), 4);
> > > + KUNIT_EXPECT_EQ(test, round_up((1 << 30) - 1, 2), 1 << 30);
> > > + KUNIT_EXPECT_EQ(test, round_up((1 << 30) - 1, 1 << 29), 1 << 30);
> > > +}
> > > +
> > > +static void round_down_test(struct kunit *test)
> > > +{
> > > + KUNIT_EXPECT_EQ(test, round_down(0, 1), 0);
> > > + KUNIT_EXPECT_EQ(test, round_down(1, 2), 0);
> > > + KUNIT_EXPECT_EQ(test, round_down(3, 2), 2);
> > > + KUNIT_EXPECT_EQ(test, round_down((1 << 30) - 1, 2), (1 << 30) - 2);
> > > + KUNIT_EXPECT_EQ(test, round_down((1 << 30) - 1, 1 << 29), 1 << 29);
> > > +}
> > > +
> > > +static void div_round_up_test(struct kunit *test)
> > > +{
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_UP(0, 1), 0);
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_UP(20, 10), 2);
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_UP(21, 10), 3);
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_UP(21, 20), 2);
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_UP(21, 99), 1);
> > > +}
> > > +
> > > +static void div_round_closest_test(struct kunit *test)
> > > +{
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_CLOSEST(0, 1), 0);
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_CLOSEST(20, 10), 2);
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_CLOSEST(21, 10), 2);
> > > + KUNIT_EXPECT_EQ(test, DIV_ROUND_CLOSEST(25, 10), 3);
> > > +}
> > > +
> > > +/* Generic test case for unsigned long inputs. */
> > > +struct test_case {
> > > + unsigned long a, b;
> > > + unsigned long result;
> > > +};
> > > +
> > > +static struct test_case gcd_cases[] = {
> > > + {
> > > + .a = 0, .b = 0,
> > > + .result = 0,
> > > + },
> > > + {
> > > + .a = 0, .b = 1,
> > > + .result = 1,
> > > + },
> > > + {
> > > + .a = 2, .b = 2,
> > > + .result = 2,
> > > + },
> > > + {
> > > + .a = 2, .b = 4,
> > > + .result = 2,
> > > + },
> > > + {
> > > + .a = 3, .b = 5,
> > > + .result = 1,
> > > + },
> > > + {
> > > + .a = 3 * 9, .b = 3 * 5,
> > > + .result = 3,
> > > + },
> > > + {
> > > + .a = 3 * 5 * 7, .b = 3 * 5 * 11,
> > > + .result = 15,
> > > + },
> > > + {
> > > + .a = 1 << 21,
> > > + .b = (1 << 21) - 1,
> > > + .result = 1,
> > > + },
> > > +};
> > > +
> > > +KUNIT_ARRAY_PARAM(gcd, gcd_cases, NULL);
> > > +
> > > +static void gcd_test(struct kunit *test)
> > > +{
> > > + const char *message_fmt = "gcd(%lu, %lu)";
> > > + const struct test_case *test_param = test->param_value;
> > > +
> > > + KUNIT_EXPECT_EQ_MSG(test, test_param->result,
> > > + gcd(test_param->a, test_param->b),
> > > + message_fmt, test_param->a,
> > > + test_param->b);
> > > +
> > > + if (test_param->a == test_param->b)
> > > + return;
> > > +
> > > + /* gcd(a,b) == gcd(b,a) */
> > > + KUNIT_EXPECT_EQ_MSG(test, test_param->result,
> > > + gcd(test_param->b, test_param->a),
> > > + message_fmt, test_param->b,
> > > + test_param->a);
> > > +}
> > > +
> > > +static struct test_case lcm_cases[] = {
> > > + {
> > > + .a = 0, .b = 0,
> > > + .result = 0,
> > > + },
> > > + {
> > > + .a = 0, .b = 1,
> > > + .result = 0,
> > > + },
> > > + {
> > > + .a = 1, .b = 2,
> > > + .result = 2,
> > > + },
> > > + {
> > > + .a = 2, .b = 2,
> > > + .result = 2,
> > > + },
> > > + {
> > > + .a = 3 * 5, .b = 3 * 7,
> > > + .result = 3 * 5 * 7,
> > > + },
> > > +};
> > > +
> > > +KUNIT_ARRAY_PARAM(lcm, lcm_cases, NULL);
> > > +
> > > +static void lcm_test(struct kunit *test)
> > > +{
> > > + const char *message_fmt = "lcm(%lu, %lu)";
> > > + const struct test_case *test_param = test->param_value;
> > > +
> > > + KUNIT_EXPECT_EQ_MSG(test, test_param->result,
> > > + lcm(test_param->a, test_param->b),
> > > + message_fmt, test_param->a,
> > > + test_param->b);
> > > +
> > > + if (test_param->a == test_param->b)
> > > + return;
> > > +
> > > + /* lcm(a,b) == lcm(b,a) */
> > > + KUNIT_EXPECT_EQ_MSG(test, test_param->result,
> > > + lcm(test_param->b, test_param->a),
> > > + message_fmt, test_param->b,
> > > + test_param->a);
> > > +}
> > > +
> > > +struct u32_test_case {
> > > + u32 a, b;
> > > + u32 result;
> > > +};
> > > +
> > > +static struct u32_test_case reciprocal_div_cases[] = {
> > > + {
> > > + .a = 0, .b = 1,
> > > + .result = 0,
> > > + },
> > > + {
> > > + .a = 42, .b = 20,
> > > + .result = 2,
> > > + },
> > > + {
> > > + .a = 42, .b = 9999,
> > > + .result = 0,
> > > + },
> > > + {
> > > + .a = (1 << 16), .b = (1 << 14),
> > > + .result = 1 << 2,
> > > + },
> > > +};
> > > +
> > > +KUNIT_ARRAY_PARAM(reciprocal_div, reciprocal_div_cases, NULL);
> >
> > Is there a reason this test is using KUNIT_EXPECT_EQ_MSG() rather than
> > a get_desc function in KUNIT_ARRAY_PARAM()? I can sort-of see how the
> > former is a little simpler, so I'm not opposed to keeping it as-is,
> > but it's nice to have KUnit aware of a nicer name for the parameter if
> > all else is equal.
> > (I think there's a stronger case for keeping the gcd/lcm tests as is
> > because they actually have two checks per parameter, but even then,
> > it's not absurdly silly. And it'd be possible to have both a get_desc
> > function and use EXPECT_..._MSG() to get the best of both worlds,
> > albeit with twice as much work.)
>
> I can add in the get_desc for it if you want.
>
> That's partly a relic of the previous versions of this patchset where
> I reused the case arrays for the unary funcs as well.
> But now the unary use case has disappeared and we only need to write
> one get_desc.
>
> But yeah, given it can test two calls of gcd, I've opted to keep it
> using _MSG().
> And I figured I'd keep the reciprocal_div test the same for
> consistency (aka, I just copy-pasted it from gcd).

Btw another reason to use _MSG is that macro text gets expanded in the
EXPECT calls.
E.g.
[11:07:19] # round_down_test: EXPECTATION FAILED at lib/math/math_kunit.c:67
[11:07:19] Expected ((4) & ~((__typeof__(4))((2)-1))) == 2, but
[11:07:19] ((4) & ~((__typeof__(4))((2)-1))) == 4

(I didn't do so for the non-parameterized tests since they point to
the line number.)

So unless one makes a get_desc function for every test, we should use
_MSG variants to give a more readable "round_down(4, 2)." And the _MSG
variant is just more convenient (and amenable to copy-paste).

>
>
>
>
> >
> > > +
> > > +static void reciprocal_div_test(struct kunit *test)
> > > +{
> > > + const struct u32_test_case *test_param = test->param_value;
> > > + struct reciprocal_value rv = reciprocal_value(test_param->b);
> > > +
> > > + KUNIT_EXPECT_EQ_MSG(test, test_param->result,
> > > + reciprocal_divide(test_param->a, rv),
> > > + "reciprocal_divide(%u, %u)",
> > > + test_param->a, test_param->b);
> > > +}
> > > +
> > > +static void reciprocal_scale_test(struct kunit *test)
> > > +{
> > > + KUNIT_EXPECT_EQ(test, reciprocal_scale(0u, 100), 0u);
> > > + KUNIT_EXPECT_EQ(test, reciprocal_scale(1u, 100), 0u);
> > > + KUNIT_EXPECT_EQ(test, reciprocal_scale(1u << 4, 1 << 28), 1u);
> > > + KUNIT_EXPECT_EQ(test, reciprocal_scale(1u << 16, 1 << 28), 1u << 12);
> > > + KUNIT_EXPECT_EQ(test, reciprocal_scale(~0u, 1 << 28), (1u << 28) - 1);
> > > +}
> > > +
> > > +static struct kunit_case math_test_cases[] = {
> > > + KUNIT_CASE(abs_test),
> > > + KUNIT_CASE(int_sqrt_test),
> > > + KUNIT_CASE(round_up_test),
> > > + KUNIT_CASE(round_down_test),
> > > + KUNIT_CASE(div_round_up_test),
> > > + KUNIT_CASE(div_round_closest_test),
> > > + KUNIT_CASE_PARAM(gcd_test, gcd_gen_params),
> > > + KUNIT_CASE_PARAM(lcm_test, lcm_gen_params),
> > > + KUNIT_CASE_PARAM(reciprocal_div_test, reciprocal_div_gen_params),
> > > + KUNIT_CASE(reciprocal_scale_test),
> > > + {}
> > > +};
> > > +
> > > +static struct kunit_suite math_test_suite = {
> > > + .name = "lib-math",
> > > + .test_cases = math_test_cases,
> > > +};
> > > +
> > > +kunit_test_suites(&math_test_suite);
> > > +
> > > +MODULE_LICENSE("GPL v2");
> > >
> > > base-commit: 4fa56ad0d12e24df768c98bffe9039f915d1bc02
> > > --
> > > 2.31.1.295.g9ea45b61b8-goog
> > >