xref: /openbmc/linux/lib/test_linear_ranges.c (revision bc64f30e)
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 
range_test_get_value(struct kunit * test)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 
range_test_get_selector_high(struct kunit * test)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 
range_test_get_value_amount(struct kunit * test)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 
range_test_get_selector_low(struct kunit * test)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_LICENSE("GPL");
220