+++ /dev/null
-.. SPDX-License-Identifier: GPL-2.0
-
-============================
-Tips For Writing KUnit Tests
-============================
-
-Exiting early on failed expectations
-------------------------------------
-
-``KUNIT_EXPECT_EQ`` and friends will mark the test as failed and continue
-execution. In some cases, it's unsafe to continue and you can use the
-``KUNIT_ASSERT`` variant to exit on failure.
-
-.. code-block:: c
-
- void example_test_user_alloc_function(struct kunit *test)
- {
- void *object = alloc_some_object_for_me();
-
- /* Make sure we got a valid pointer back. */
- KUNIT_ASSERT_NOT_ERR_OR_NULL(test, object);
- do_something_with_object(object);
- }
-
-Allocating memory
------------------
-
-Where you would use ``kzalloc``, you should prefer ``kunit_kzalloc`` instead.
-KUnit will ensure the memory is freed once the test completes.
-
-This is particularly useful since it lets you use the ``KUNIT_ASSERT_EQ``
-macros to exit early from a test without having to worry about remembering to
-call ``kfree``.
-
-Example:
-
-.. code-block:: c
-
- void example_test_allocation(struct kunit *test)
- {
- char *buffer = kunit_kzalloc(test, 16, GFP_KERNEL);
- /* Ensure allocation succeeded. */
- KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buffer);
-
- KUNIT_ASSERT_STREQ(test, buffer, "");
- }
-
-
-Testing static functions
-------------------------
-
-If you don't want to expose functions or variables just for testing, one option
-is to conditionally ``#include`` the test file at the end of your .c file, e.g.
-
-.. code-block:: c
-
- /* In my_file.c */
-
- static int do_interesting_thing();
-
- #ifdef CONFIG_MY_KUNIT_TEST
- #include "my_kunit_test.c"
- #endif
-
-Injecting test-only code
-------------------------
-
-Similarly to the above, it can be useful to add test-specific logic.
-
-.. code-block:: c
-
- /* In my_file.h */
-
- #ifdef CONFIG_MY_KUNIT_TEST
- /* Defined in my_kunit_test.c */
- void test_only_hook(void);
- #else
- void test_only_hook(void) { }
- #endif
-
-This test-only code can be made more useful by accessing the current kunit
-test, see below.
-
-Accessing the current test
---------------------------
-
-In some cases, you need to call test-only code from outside the test file, e.g.
-like in the example above or if you're providing a fake implementation of an
-ops struct.
-There is a ``kunit_test`` field in ``task_struct``, so you can access it via
-``current->kunit_test``.
-
-Here's a slightly in-depth example of how one could implement "mocking":
-
-.. code-block:: c
-
- #include <linux/sched.h> /* for current */
-
- struct test_data {
- int foo_result;
- int want_foo_called_with;
- };
-
- static int fake_foo(int arg)
- {
- struct kunit *test = current->kunit_test;
- struct test_data *test_data = test->priv;
-
- KUNIT_EXPECT_EQ(test, test_data->want_foo_called_with, arg);
- return test_data->foo_result;
- }
-
- static void example_simple_test(struct kunit *test)
- {
- /* Assume priv is allocated in the suite's .init */
- struct test_data *test_data = test->priv;
-
- test_data->foo_result = 42;
- test_data->want_foo_called_with = 1;
-
- /* In a real test, we'd probably pass a pointer to fake_foo somewhere
- * like an ops struct, etc. instead of calling it directly. */
- KUNIT_EXPECT_EQ(test, fake_foo(1), 42);
- }
-
-
-Note: here we're able to get away with using ``test->priv``, but if you wanted
-something more flexible you could use a named ``kunit_resource``, see
-Documentation/dev-tools/kunit/api/test.rst.
-
-Failing the current test
-------------------------
-
-But sometimes, you might just want to fail the current test. In that case, we
-have ``kunit_fail_current_test(fmt, args...)`` which is defined in ``<kunit/test-bug.h>`` and
-doesn't require pulling in ``<kunit/test.h>``.
-
-E.g. say we had an option to enable some extra debug checks on some data structure:
-
-.. code-block:: c
-
- #include <kunit/test-bug.h>
-
- #ifdef CONFIG_EXTRA_DEBUG_CHECKS
- static void validate_my_data(struct data *data)
- {
- if (is_valid(data))
- return;
-
- kunit_fail_current_test("data %p is invalid", data);
-
- /* Normal, non-KUnit, error reporting code here. */
- }
- #else
- static void my_debug_function(void) { }
- #endif
-
-
-Customizing error messages
---------------------------
-
-Each of the ``KUNIT_EXPECT`` and ``KUNIT_ASSERT`` macros have a ``_MSG`` variant.
-These take a format string and arguments to provide additional context to the automatically generated error messages.
-
-.. code-block:: c
-
- char some_str[41];
- generate_sha1_hex_string(some_str);
-
- /* Before. Not easy to tell why the test failed. */
- KUNIT_EXPECT_EQ(test, strlen(some_str), 40);
-
- /* After. Now we see the offending string. */
- KUNIT_EXPECT_EQ_MSG(test, strlen(some_str), 40, "some_str='%s'", some_str);
-
-Alternatively, one can take full control over the error message by using ``KUNIT_FAIL()``, e.g.
-
-.. code-block:: c
-
- /* Before */
- KUNIT_EXPECT_EQ(test, some_setup_function(), 0);
-
- /* After: full control over the failure message. */
- if (some_setup_function())
- KUNIT_FAIL(test, "Failed to setup thing for testing");
-
-Next Steps
-==========
-* Optional: see the Documentation/dev-tools/kunit/usage.rst page for a more
- in-depth explanation of KUnit.
projects / linux-2.6-microblaze.git / commitdiff