[PATCH 8/9] kunit: Add example parameterized test with direct dynamic parameter array setup

[Marie Zhussupova <marievic@google.com>]

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. It highlights the
use of `param_init` and `param_exit` for proper initialization and
cleanup, and their registration to the test with
`KUNIT_CASE_PARAM_WITH_INIT`.

Signed-off-by: Marie Zhussupova <marievic@google.com>
---
 lib/kunit/kunit-example-test.c | 95 ++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c
index 5bf559e243f6..3ab121d81bf6 100644
--- a/lib/kunit/kunit-example-test.c
+++ b/lib/kunit/kunit-example-test.c
@@ -387,6 +387,98 @@ 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 typically only provides the immediately 'prev' parameter, while
+ * Fibonacci requires access to two preceding values for calculation.
+ */
+static void *make_fibonacci_params(int seq_size)
+{
+	int *seq;
+
+	if (seq_size <= 0)
+		return NULL;
+
+	seq = kmalloc_array(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(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 init function that registers a dynamic array.
+ */
+static int example_param_init_dynamic_arr(struct kunit *test)
+{
+	int seq_size = 6;
+	int *fibonacci_params = make_fibonacci_params(seq_size);
+
+	if (!fibonacci_params)
+		return -ENOMEM;
+
+	/*
+	 * Passes the dynamic parameter array information to the parent struct kunit.
+	 * The array and its metadata will be stored in test->parent->params_data.
+	 * The array itself will be located in params_data.params.
+	 */
+	kunit_register_params_array(test, fibonacci_params, seq_size,
+				    example_param_dynamic_arr_get_desc);
+	return 0;
+}
+
+/**
+ * Function to clean up the parameterized test's parent kunit struct if
+ * there were custom allocations.
+ */
+static void example_param_exit_dynamic_arr(struct kunit *test)
+{
+	/*
+	 * We allocated this array, so we need to free it.
+	 * Since the parent parameter instance is passed here,
+	 * we can directly access the array via `test->params_data.params`
+	 * instead of `test->parent->params_data.params`.
+	 */
+	kfree(test->params_data.params);
+}
+
+/*
+ * 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.
@@ -408,6 +500,9 @@ 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, NULL,
 				   example_param_init, NULL),
+	KUNIT_CASE_PARAM_WITH_INIT(example_params_test_with_init_dynamic_arr, NULL,
+				   example_param_init_dynamic_arr,
+				   example_param_exit_dynamic_arr),
 	KUNIT_CASE_SLOW(example_slow_test),
 	{}
 };
-- 
2.50.1.552.g942d659e1b-goog