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| -rw-r--r-- | Documentation/dev-tools/kunit/tips.rst | 78 |
1 files changed, 76 insertions, 2 deletions
diff --git a/Documentation/dev-tools/kunit/tips.rst b/Documentation/dev-tools/kunit/tips.rst index a6ca0af14098..8d8c238f7f79 100644 --- a/Documentation/dev-tools/kunit/tips.rst +++ b/Documentation/dev-tools/kunit/tips.rst @@ -78,8 +78,82 @@ Similarly to the above, it can be useful to add test-specific logic. void test_only_hook(void) { } #endif -TODO(dlatypov@google.com): add an example of using ``current->kunit_test`` in -such a hook when it's not only updated for ``CONFIG_KASAN=y``. +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 :doc:`api/test`. + +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 -------------------------- |