lib/test_linear_ranges.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * KUnit test for the linear_ranges helper.
   4  *
   5  * Copyright (C) 2020, ROHM Semiconductors.
   6  * Author: Matti Vaittinen <matti.vaittien@fi.rohmeurope.com>
   7  */
   8 #include <kunit/test.h>
   9
  10 #include <linux/linear_range.h>
  11
  12 /* First things first. I deeply dislike unit-tests. I have seen all the hell
  13  * breaking loose when people who think the unit tests are "the silver bullet"
  14  * to kill bugs get to decide how a company should implement testing strategy...
  15  *
  16  * Believe me, it may get _really_ ridiculous. It is tempting to think that
  17  * walking through all the possible execution branches will nail down 100% of
  18  * bugs. This may lead to ideas about demands to get certain % of "test
  19  * coverage" - measured as line coverage. And that is one of the worst things
  20  * you can do.
  21  *
  22  * Ask people to provide line coverage and they do. I've seen clever tools
  23  * which generate test cases to test the existing functions - and by default
  24  * these tools expect code to be correct and just generate checks which are
  25  * passing when ran against current code-base. Run this generator and you'll get
  26  * tests that do not test code is correct but just verify nothing changes.
  27  * Problem is that testing working code is pointless. And if it is not
  28  * working, your test must not assume it is working. You won't catch any bugs
  29  * by such tests. What you can do is to generate a huge amount of tests.
  30  * Especially if you were are asked to proivde 100% line-coverage x_x. So what
  31  * does these tests - which are not finding any bugs now - do?
  32  *
  33  * They add inertia to every future development. I think it was Terry Pratchet
  34  * who wrote someone having same impact as thick syrup has to chronometre.
  35  * Excessive amount of unit-tests have this effect to development. If you do
  36  * actually find _any_ bug from code in such environment and try fixing it...
  37  * ...chances are you also need to fix the test cases. In sunny day you fix one
  38  * test. But I've done refactoring which resulted 500+ broken tests (which had
  39  * really zero value other than proving to managers that we do do "quality")...
  40  *
  41  * After this being said - there are situations where UTs can be handy. If you
  42  * have algorithms which take some input and should produce output - then you
  43  * can implement few, carefully selected simple UT-cases which test this. I've
  44  * previously used this for example for netlink and device-tree data parsing
  45  * functions. Feed some data examples to functions and verify the output is as
  46  * expected. I am not covering all the cases but I will see the logic should be
  47  * working.
  48  *
  49  * Here we also do some minor testing. I don't want to go through all branches
  50  * or test more or less obvious things - but I want to see the main logic is
  51  * working. And I definitely don't want to add 500+ test cases that break when
  52  * some simple fix is done x_x. So - let's only add few, well selected tests
  53  * which ensure as much logic is good as possible.
  54  */
  55
  56 /*
  57  * Test Range 1:
  58  * selectors:   2       3       4       5       6
  59  * values (5):  10      20      30      40      50
  60  *
  61  * Test Range 2:
  62  * selectors:   7       8       9       10
  63  * values (4):  100     150     200     250
  64  */
  65
  66 #define RANGE1_MIN 10
  67 #define RANGE1_MIN_SEL 2
  68 #define RANGE1_STEP 10
  69
  70 /* 2, 3, 4, 5, 6 */
  71 static const unsigned int range1_sels[] = { RANGE1_MIN_SEL, RANGE1_MIN_SEL + 1,
  72                                             RANGE1_MIN_SEL + 2,
  73                                             RANGE1_MIN_SEL + 3,
  74                                             RANGE1_MIN_SEL + 4 };
  75 /* 10, 20, 30, 40, 50 */
  76 static const unsigned int range1_vals[] = { RANGE1_MIN, RANGE1_MIN +
  77                                             RANGE1_STEP,
  78                                             RANGE1_MIN + RANGE1_STEP * 2,
  79                                             RANGE1_MIN + RANGE1_STEP * 3,
  80                                             RANGE1_MIN + RANGE1_STEP * 4 };
  81
  82 #define RANGE2_MIN 100
  83 #define RANGE2_MIN_SEL 7
  84 #define RANGE2_STEP 50
  85
  86 /*  7, 8, 9, 10 */
  87 static const unsigned int range2_sels[] = { RANGE2_MIN_SEL, RANGE2_MIN_SEL + 1,
  88                                             RANGE2_MIN_SEL + 2,
  89                                             RANGE2_MIN_SEL + 3 };
  90 /* 100, 150, 200, 250 */
  91 static const unsigned int range2_vals[] = { RANGE2_MIN, RANGE2_MIN +
  92                                             RANGE2_STEP,
  93                                             RANGE2_MIN + RANGE2_STEP * 2,
  94                                             RANGE2_MIN + RANGE2_STEP * 3 };
  95
  96 #define RANGE1_NUM_VALS (ARRAY_SIZE(range1_vals))
  97 #define RANGE2_NUM_VALS (ARRAY_SIZE(range2_vals))
  98 #define RANGE_NUM_VALS (RANGE1_NUM_VALS + RANGE2_NUM_VALS)
  99
 100 #define RANGE1_MAX_SEL (RANGE1_MIN_SEL + RANGE1_NUM_VALS - 1)
 101 #define RANGE1_MAX_VAL (range1_vals[RANGE1_NUM_VALS - 1])
 102
 103 #define RANGE2_MAX_SEL (RANGE2_MIN_SEL + RANGE2_NUM_VALS - 1)
 104 #define RANGE2_MAX_VAL (range2_vals[RANGE2_NUM_VALS - 1])
 105
 106 #define SMALLEST_SEL RANGE1_MIN_SEL
 107 #define SMALLEST_VAL RANGE1_MIN
 108
 109 static struct linear_range testr[] = {
 110         LINEAR_RANGE(RANGE1_MIN, RANGE1_MIN_SEL, RANGE1_MAX_SEL, RANGE1_STEP),
 111         LINEAR_RANGE(RANGE2_MIN, RANGE2_MIN_SEL, RANGE2_MAX_SEL, RANGE2_STEP),
 112 };
 113
 114 static void range_test_get_value(struct kunit *test)
 115 {
 116         int ret, i;
 117         unsigned int sel, val;
 118
 119         for (i = 0; i < RANGE1_NUM_VALS; i++) {
 120                 sel = range1_sels[i];
 121                 ret = linear_range_get_value_array(&testr[0], 2, sel, &val);
 122                 KUNIT_EXPECT_EQ(test, 0, ret);
 123                 KUNIT_EXPECT_EQ(test, val, range1_vals[i]);
 124         }
 125         for (i = 0; i < RANGE2_NUM_VALS; i++) {
 126                 sel = range2_sels[i];
 127                 ret = linear_range_get_value_array(&testr[0], 2, sel, &val);
 128                 KUNIT_EXPECT_EQ(test, 0, ret);
 129                 KUNIT_EXPECT_EQ(test, val, range2_vals[i]);
 130         }
 131         ret = linear_range_get_value_array(&testr[0], 2, sel + 1, &val);
 132         KUNIT_EXPECT_NE(test, 0, ret);
 133 }
 134
 135 static void range_test_get_selector_high(struct kunit *test)
 136 {
 137         int ret, i;
 138         unsigned int sel;
 139         bool found;
 140
 141         for (i = 0; i < RANGE1_NUM_VALS; i++) {
 142                 ret = linear_range_get_selector_high(&testr[0], range1_vals[i],
 143                                                      &sel, &found);
 144                 KUNIT_EXPECT_EQ(test, 0, ret);
 145                 KUNIT_EXPECT_EQ(test, sel, range1_sels[i]);
 146                 KUNIT_EXPECT_TRUE(test, found);
 147         }
 148
 149         ret = linear_range_get_selector_high(&testr[0], RANGE1_MAX_VAL + 1,
 150                                              &sel, &found);
 151         KUNIT_EXPECT_LE(test, ret, 0);
 152
 153         ret = linear_range_get_selector_high(&testr[0], RANGE1_MIN - 1,
 154                                              &sel, &found);
 155         KUNIT_EXPECT_EQ(test, 0, ret);
 156         KUNIT_EXPECT_FALSE(test, found);
 157         KUNIT_EXPECT_EQ(test, sel, range1_sels[0]);
 158 }
 159
 160 static void range_test_get_value_amount(struct kunit *test)
 161 {
 162         int ret;
 163
 164         ret = linear_range_values_in_range_array(&testr[0], 2);
 165         KUNIT_EXPECT_EQ(test, (int)RANGE_NUM_VALS, ret);
 166 }
 167
 168 static void range_test_get_selector_low(struct kunit *test)
 169 {
 170         int i, ret;
 171         unsigned int sel;
 172         bool found;
 173
 174         for (i = 0; i < RANGE1_NUM_VALS; i++) {
 175                 ret = linear_range_get_selector_low_array(&testr[0], 2,
 176                                                           range1_vals[i], &sel,
 177                                                           &found);
 178                 KUNIT_EXPECT_EQ(test, 0, ret);
 179                 KUNIT_EXPECT_EQ(test, sel, range1_sels[i]);
 180                 KUNIT_EXPECT_TRUE(test, found);
 181         }
 182         for (i = 0; i < RANGE2_NUM_VALS; i++) {
 183                 ret = linear_range_get_selector_low_array(&testr[0], 2,
 184                                                           range2_vals[i], &sel,
 185                                                           &found);
 186                 KUNIT_EXPECT_EQ(test, 0, ret);
 187                 KUNIT_EXPECT_EQ(test, sel, range2_sels[i]);
 188                 KUNIT_EXPECT_TRUE(test, found);
 189         }
 190
 191         /*
 192          * Seek value greater than range max => get_selector_*_low should
 193          * return Ok - but set found to false as value is not in range
 194          */
 195         ret = linear_range_get_selector_low_array(&testr[0], 2,
 196                                         range2_vals[RANGE2_NUM_VALS - 1] + 1,
 197                                         &sel, &found);
 198
 199         KUNIT_EXPECT_EQ(test, 0, ret);
 200         KUNIT_EXPECT_EQ(test, sel, range2_sels[RANGE2_NUM_VALS - 1]);
 201         KUNIT_EXPECT_FALSE(test, found);
 202 }
 203
 204 static struct kunit_case range_test_cases[] = {
 205         KUNIT_CASE(range_test_get_value_amount),
 206         KUNIT_CASE(range_test_get_selector_high),
 207         KUNIT_CASE(range_test_get_selector_low),
 208         KUNIT_CASE(range_test_get_value),
 209         {},
 210 };
 211
 212 static struct kunit_suite range_test_module = {
 213         .name = "linear-ranges-test",
 214         .test_cases = range_test_cases,
 215 };
 216
 217 kunit_test_suites(&range_test_module);
 218
 219 MODULE_DESCRIPTION("KUnit test for the linear_ranges helper");
 220 MODULE_LICENSE("GPL");