[PATCH v2 6/7] kunit: Add example parameterized test with direct dynamic parameter array setup

[David Gow]

On Tue, 12 Aug 2025 at 06:18, Marie Zhussupova <marievic at google.com> wrote:
>
> Introduce example_params_test_with_init_dynamic_arr(). This new
> KUnit test demonstrates directly assigning a dynamic parameter
> array, using the kunit_register_params_array() macro, to a
> parameterized test context.
>
> It highlights the use of param_init() and param_exit() for
> initialization and exit of a parameterized test, and their
> registration to the test case with KUNIT_CASE_PARAM_WITH_INIT().
>
> Signed-off-by: Marie Zhussupova <marievic at google.com>
> ---

I really like this example now. Thanks!

Reviewed-by: David Gow <davidgow at google.com>

Cheers,
-- David


>
> Changes in v2:
>
> - kunit_array_gen_params() is now explicitly passed to
>   KUNIT_CASE_PARAM_WITH_INIT() to be consistent with
>   the parameterized test being defined by the existence
>   of the generate_params() function.
> - param_init() was changed to output a log at the start
>   of a parameterized test.
> - The parameter array was changed to be allocated
>   using kunit_kmalloc_array(), a KUnit memory allocation
>   API, as that would be the preferred/easier method. To
>   still demonstrate a use of param_exit(), it now outputs
>   a log at the end of the parameterized test.
> - The comments and the commit message were changed to
>   reflect the parameterized testing terminology. See
>   the patch series cover letter change log for the
>   definitions.
>
> ---
>  lib/kunit/kunit-example-test.c | 104 +++++++++++++++++++++++++++++++++
>  1 file changed, 104 insertions(+)
>
> diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c
> index f2819ee58965..ff21511889a4 100644
> --- a/lib/kunit/kunit-example-test.c
> +++ b/lib/kunit/kunit-example-test.c
> @@ -393,6 +393,107 @@ static void example_params_test_with_init(struct kunit *test)
>         kunit_put_resource(res);
>  }
>
> +/*
> + * Helper function to create a parameter array of Fibonacci numbers. This example
> + * highlights a parameter generation scenario that is:
> + * 1. Not feasible to fully pre-generate at compile time.
> + * 2. Challenging to implement with a standard generate_params() function,
> + * as it only provides the previous parameter, while Fibonacci requires
> + * access to two preceding values for calculation.
> + */
> +static void *make_fibonacci_params(struct kunit *test, size_t seq_size)
> +{
> +       int *seq;
> +
> +       if (seq_size <= 0)
> +               return NULL;
> +       /*
> +        * Using kunit_kmalloc_array here ties the lifetime of the array to
> +        * the parameterized test i.e. it will get automatically cleaned up
> +        * by KUnit after the parameterized test finishes.
> +        */
> +       seq = kunit_kmalloc_array(test, seq_size, sizeof(int), GFP_KERNEL);
> +
> +       if (!seq)
> +               return NULL;
> +       if (seq_size >= 1)
> +               seq[0] = 0;
> +       if (seq_size >= 2)
> +               seq[1] = 1;
> +       for (int i = 2; i < seq_size; i++)
> +               seq[i] = seq[i - 1] + seq[i - 2];
> +       return seq;
> +}
> +
> +/*
> + * This is an example of a function that provides a description for each of the
> + * parameters.
> + */
> +static void example_param_dynamic_arr_get_desc(struct kunit *test, const void *p, char *desc)
> +{
> +       const int *fib_num = p;
> +
> +       snprintf(desc, KUNIT_PARAM_DESC_SIZE, "fibonacci param: %d", *fib_num);
> +}
> +
> +/*
> + * Example of a parameterized test param_init() function that registers a dynamic
> + * array of parameters.
> + */
> +static int example_param_init_dynamic_arr(struct kunit *test)
> +{
> +       size_t seq_size;
> +       int *fibonacci_params;
> +
> +       kunit_info(test, "initializing parameterized test\n");
> +
> +       seq_size = 6;
> +       fibonacci_params = make_fibonacci_params(test, seq_size);
> +
> +       if (!fibonacci_params)
> +               return -ENOMEM;
> +
> +       /*
> +        * Passes the dynamic parameter array information to the parameterized test
> +        * context struct kunit. The array and its metadata will be stored in
> +        * test->parent->params_array. The array itself will be located in
> +        * params_data.params.
> +        *
> +        * Note that you will need to pass kunit_array_gen_params() as the
> +        * generator function to KUNIT_CASE_PARAM_WITH_INIT() when registering
> +        * a parameter array this route.
> +        */
> +       kunit_register_params_array(test, fibonacci_params, seq_size,
> +                                   example_param_dynamic_arr_get_desc);
> +       return 0;
> +}
> +
> +/*
> + * Example of a parameterized test param_exit() function that outputs a log
> + * at the end of the parameterized test. It could also be used for any other
> + * teardown logic.
> + */
> +static void example_param_exit_dynamic_arr(struct kunit *test)
> +{
> +       kunit_info(test, "exiting parameterized test\n");
> +}
> +
> +/*
> + * Example of test that uses the registered dynamic array to perform assertions
> + * and expectations.
> + */
> +static void example_params_test_with_init_dynamic_arr(struct kunit *test)
> +{
> +       const int *param = test->param_value;
> +       int param_val;
> +
> +       /* By design, param pointer will not be NULL. */
> +       KUNIT_ASSERT_NOT_NULL(test, param);
> +
> +       param_val = *param;
> +       KUNIT_EXPECT_EQ(test, param_val - param_val, 0);
> +}
> +
>  /*
>   * Here we make a list of all the test cases we want to add to the test suite
>   * below.
> @@ -414,6 +515,9 @@ static struct kunit_case example_test_cases[] = {
>         KUNIT_CASE_PARAM(example_params_test, example_gen_params),
>         KUNIT_CASE_PARAM_WITH_INIT(example_params_test_with_init, kunit_array_gen_params,
>                                    example_param_init, NULL),
> +       KUNIT_CASE_PARAM_WITH_INIT(example_params_test_with_init_dynamic_arr,
> +                                  kunit_array_gen_params, example_param_init_dynamic_arr,
> +                                  example_param_exit_dynamic_arr),
>         KUNIT_CASE_SLOW(example_slow_test),
>         {}
>  };
> --
> 2.51.0.rc0.205.g4a044479a3-goog
>
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