lib/test_string.c: add strspn and strcspn tests

Before refactoring strspn() and strcspn(), add some simple test cases.

Link: https://lkml.kernel.org/r/20220328224119.3003834-1-linux@rasmusvillemoes.dkSigned-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andy@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

lib/test_string.c

@@ -179,6 +179,34 @@ static __init int strnchr_selftest(void)
 	return 0;
 }
 
+static __init int strspn_selftest(void)
+{
+	static const struct strspn_test {
+		const char str[16];
+		const char accept[16];
+		const char reject[16];
+		unsigned a;
+		unsigned r;
+	} tests[] __initconst = {
+		{ "foobar", "", "", 0, 6 },
+		{ "abba", "abc", "ABBA", 4, 4 },
+		{ "abba", "a", "b", 1, 1 },
+		{ "", "abc", "abc", 0, 0},
+	};
+	const struct strspn_test *s = tests;
+	size_t i, res;
+
+	for (i = 0; i < ARRAY_SIZE(tests); ++i, ++s) {
+		res = strspn(s->str, s->accept);
+		if (res != s->a)
+			return 0x100 + 2*i;
+		res = strcspn(s->str, s->reject);
+		if (res != s->r)
+			return 0x100 + 2*i + 1;
+	}
+	return 0;
+}
+
 static __exit void string_selftest_remove(void)
 {
 }
@@ -212,6 +240,11 @@ static __init int string_selftest_init(void)
 	if (subtest)
 		goto fail;
 
+	test = 6;
+	subtest = strspn_selftest();
+	if (subtest)
+		goto fail;
+
 	pr_info("String selftests succeeded\n");
 	return 0;
 fail: