[PATCH v4 1/2] kunit: Support for Parameterized Testing

[Arpitha Raghunandan <98.arpi@gmail.com>]

Implementation of support for parameterized testing in KUnit.
This approach requires the creation of a test case using the
KUNIT_CASE_PARAM macro that accepts a generator function as input.
This generator function should return the next parameter given the
previous parameter in parameterized tests. It also provides
a macro to generate common-case generators.

Signed-off-by: Arpitha Raghunandan <98.arpi@gmail.com>
Co-developed-by: Marco Elver <elver@google.com>
Signed-off-by: Marco Elver <elver@google.com>
---
Changes v3->v4:
- Rename kunit variables
- Rename generator function helper macro
- Add documentation for generator approach
- Display test case name in case of failure along with param index
Changes v2->v3:
- Modifictaion of generator macro and method
Changes v1->v2:
- Use of a generator method to access test case parameters

 include/kunit/test.h | 34 ++++++++++++++++++++++++++++++++++
 lib/kunit/test.c     | 21 ++++++++++++++++++++-
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/include/kunit/test.h b/include/kunit/test.h
index 9197da792336..ec2307ee9bb0 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -107,6 +107,13 @@ struct kunit;
  *
  * @run_case: the function representing the actual test case.
  * @name:     the name of the test case.
+ * @generate_params: the generator function for parameterized tests.
+ *
+ * The generator function is used to lazily generate a series of
+ * arbitrarily typed values that fit into a void*. The argument @prev
+ * is the previously returned value, which should be used to derive the
+ * next value; @prev is set to NULL on the initial generator call.
+ * When no more values are available, the generator must return NULL.
  *
  * A test case is a function with the signature,
  * ``void (*)(struct kunit *)``
@@ -141,6 +148,7 @@ struct kunit;
 struct kunit_case {
 	void (*run_case)(struct kunit *test);
 	const char *name;
+	void* (*generate_params)(void *prev);
 
 	/* private: internal use only. */
 	bool success;
@@ -162,6 +170,9 @@ static inline char *kunit_status_to_string(bool status)
  * &struct kunit_case for an example on how to use it.
  */
 #define KUNIT_CASE(test_name) { .run_case = test_name, .name = #test_name }
+#define KUNIT_CASE_PARAM(test_name, gen_params)			\
+		{ .run_case = test_name, .name = #test_name,	\
+		  .generate_params = gen_params }
 
 /**
  * struct kunit_suite - describes a related collection of &struct kunit_case
@@ -208,6 +219,15 @@ struct kunit {
 	const char *name; /* Read only after initialization! */
 	char *log; /* Points at case log after initialization */
 	struct kunit_try_catch try_catch;
+	/* param_value points to test case parameters in parameterized tests */
+	void *param_value;
+	/*
+	 * param_index stores the index of the parameter in
+	 * parameterized tests. param_index + 1 is printed
+	 * to indicate the parameter that causes the test
+	 * to fail in case of test failure.
+	 */
+	int param_index;
 	/*
 	 * success starts as true, and may only be set to false during a
 	 * test case; thus, it is safe to update this across multiple
@@ -1742,4 +1762,18 @@ do {									       \
 						fmt,			       \
 						##__VA_ARGS__)
 
+/**
+ * KUNIT_ARRAY_PARAM() - Helper method for test parameter generators
+ * 			 required in parameterized tests.
+ * @name:  prefix of the name for the test parameter generator function.
+ *	   It will be suffixed by "_gen_params".
+ * @array: a user-supplied pointer to an array of test parameters.
+ */
+#define KUNIT_ARRAY_PARAM(name, array)								\
+	static void *name##_gen_params(void *prev)						\
+	{											\
+		typeof((array)[0]) * __next = prev ? ((typeof(__next)) prev) + 1 : (array);	\
+		return __next - (array) < ARRAY_SIZE((array)) ? __next : NULL;			\
+	}
+
 #endif /* _KUNIT_TEST_H */
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index 750704abe89a..8ad908b61494 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -127,6 +127,12 @@ unsigned int kunit_test_case_num(struct kunit_suite *suite,
 }
 EXPORT_SYMBOL_GPL(kunit_test_case_num);
 
+static void kunit_print_failed_param(struct kunit *test)
+{
+	kunit_err(test, "\n\tTest failed at:\n\ttest case: %s\n\tparameter: %d\n",
+						test->name, test->param_index + 1);
+}
+
 static void kunit_print_string_stream(struct kunit *test,
 				      struct string_stream *stream)
 {
@@ -168,6 +174,8 @@ static void kunit_fail(struct kunit *test, struct kunit_assert *assert)
 	assert->format(assert, stream);
 
 	kunit_print_string_stream(test, stream);
+	if (test->param_value)
+		kunit_print_failed_param(test);
 
 	WARN_ON(string_stream_destroy(stream));
 }
@@ -239,7 +247,18 @@ static void kunit_run_case_internal(struct kunit *test,
 		}
 	}
 
-	test_case->run_case(test);
+	if (!test_case->generate_params) {
+		test_case->run_case(test);
+	} else {
+		test->param_value = test_case->generate_params(NULL);
+		test->param_index = 0;
+
+		while (test->param_value) {
+			test_case->run_case(test);
+			test->param_value = test_case->generate_params(test->param_value);
+			test->param_index++;
+		}
+	}
 }
 
 static void kunit_case_internal_cleanup(struct kunit *test)
-- 
2.25.1