// SPDX-License-Identifier: GPL-2.0 /* * KUnit test for the linear_ranges helper. * * Copyright (C) 2020, ROHM Semiconductors. * Author: Matti Vaittinen <[email protected]> */ #include <kunit/test.h> #include <linux/linear_range.h> /* First things first. I deeply dislike unit-tests. I have seen all the hell * breaking loose when people who think the unit tests are "the silver bullet" * to kill bugs get to decide how a company should implement testing strategy... * * Believe me, it may get _really_ ridiculous. It is tempting to think that * walking through all the possible execution branches will nail down 100% of * bugs. This may lead to ideas about demands to get certain % of "test * coverage" - measured as line coverage. And that is one of the worst things * you can do. * * Ask people to provide line coverage and they do. I've seen clever tools * which generate test cases to test the existing functions - and by default * these tools expect code to be correct and just generate checks which are * passing when ran against current code-base. Run this generator and you'll get * tests that do not test code is correct but just verify nothing changes. * Problem is that testing working code is pointless. And if it is not * working, your test must not assume it is working. You won't catch any bugs * by such tests. What you can do is to generate a huge amount of tests. * Especially if you were are asked to proivde 100% line-coverage x_x. So what * does these tests - which are not finding any bugs now - do? * * They add inertia to every future development. I think it was Terry Pratchet * who wrote someone having same impact as thick syrup has to chronometre. * Excessive amount of unit-tests have this effect to development. If you do * actually find _any_ bug from code in such environment and try fixing it... * ...chances are you also need to fix the test cases. In sunny day you fix one * test. But I've done refactoring which resulted 500+ broken tests (which had * really zero value other than proving to managers that we do do "quality")... * * After this being said - there are situations where UTs can be handy. If you * have algorithms which take some input and should produce output - then you * can implement few, carefully selected simple UT-cases which test this. I've * previously used this for example for netlink and device-tree data parsing * functions. Feed some data examples to functions and verify the output is as * expected. I am not covering all the cases but I will see the logic should be * working. * * Here we also do some minor testing. I don't want to go through all branches * or test more or less obvious things - but I want to see the main logic is * working. And I definitely don't want to add 500+ test cases that break when * some simple fix is done x_x. So - let's only add few, well selected tests * which ensure as much logic is good as possible. */ /* * Test Range 1: * selectors: 2 3 4 5 6 * values (5): 10 20 30 40 50 * * Test Range 2: * selectors: 7 8 9 10 * values (4): 100 150 200 250 */ #define RANGE1_MIN … #define RANGE1_MIN_SEL … #define RANGE1_STEP … /* 2, 3, 4, 5, 6 */ static const unsigned int range1_sels[] = …; /* 10, 20, 30, 40, 50 */ static const unsigned int range1_vals[] = …; #define RANGE2_MIN … #define RANGE2_MIN_SEL … #define RANGE2_STEP … /* 7, 8, 9, 10 */ static const unsigned int range2_sels[] = …; /* 100, 150, 200, 250 */ static const unsigned int range2_vals[] = …; #define RANGE1_NUM_VALS … #define RANGE2_NUM_VALS … #define RANGE_NUM_VALS … #define RANGE1_MAX_SEL … #define RANGE1_MAX_VAL … #define RANGE2_MAX_SEL … #define RANGE2_MAX_VAL … #define SMALLEST_SEL … #define SMALLEST_VAL … static struct linear_range testr[] = …; static void range_test_get_value(struct kunit *test) { … } static void range_test_get_selector_high(struct kunit *test) { … } static void range_test_get_value_amount(struct kunit *test) { … } static void range_test_get_selector_low(struct kunit *test) { … } static struct kunit_case range_test_cases[] = …; static struct kunit_suite range_test_module = …; kunit_test_suites(…); MODULE_DESCRIPTION(…) …; MODULE_LICENSE(…) …;
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