[PATCH v5 5/5] smb/client: introduce KUnit test to check search result of smb2_error_map_table

[chenxiaosong.chenxiaosong@linux.dev]

From: ChenXiaoSong <chenxiaosong@kylinos.cn>

The KUnit test are executed when cifs.ko is loaded.

Just like `fs/ext4/mballoc.c` includes `fs/ext4/mballoc-test.c`.
`smb2maperror.c` also includes `smb2maperror_test.c`, allowing KUnit
tests to access any functions and variables in `smb2maperror.c`.

The maperror_test_check_search() checks whether all elements can be
correctly found in the array.

Signed-off-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/Kconfig                    | 17 +++++++++++
 fs/smb/client/smb2maperror.c      |  4 +++
 fs/smb/client/smb2maperror_test.c | 48 +++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+)
 create mode 100644 fs/smb/client/smb2maperror_test.c

diff --git a/fs/smb/Kconfig b/fs/smb/Kconfig
index ef425789fa6a..85f7ad5fbc5e 100644
--- a/fs/smb/Kconfig
+++ b/fs/smb/Kconfig
@@ -9,3 +9,20 @@ config SMBFS
 	tristate
 	default y if CIFS=y || SMB_SERVER=y
 	default m if CIFS=m || SMB_SERVER=m
+
+config SMB_KUNIT_TESTS
+	tristate "KUnit tests for SMB" if !KUNIT_ALL_TESTS
+	depends on SMBFS && KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the SMB KUnit tests.
+
+	  KUnit tests run during boot and output the results to the debug log
+	  in TAP format (https://testanything.org/). Only useful for kernel devs
+	  running KUnit test harness and are not for inclusion into a production
+	  build.
+
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
diff --git a/fs/smb/client/smb2maperror.c b/fs/smb/client/smb2maperror.c
index e47564cc3a04..e71ee23400e8 100644
--- a/fs/smb/client/smb2maperror.c
+++ b/fs/smb/client/smb2maperror.c
@@ -114,3 +114,7 @@ int smb2_init_maperror(void)
 
 	return 0;
 }
+
+#if IS_ENABLED(CONFIG_SMB_KUNIT_TESTS)
+#include "smb2maperror_test.c"
+#endif /* CONFIG_SMB_KUNIT_TESTS */
diff --git a/fs/smb/client/smb2maperror_test.c b/fs/smb/client/smb2maperror_test.c
new file mode 100644
index 000000000000..bb2ae4f32611
--- /dev/null
+++ b/fs/smb/client/smb2maperror_test.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ *
+ *   KUnit tests of SMB2 maperror
+ *
+ *   Copyright (C) 2025 KylinSoft Co., Ltd. All rights reserved.
+ *   Author(s): ChenXiaoSong <chenxiaosong@kylinos.cn>
+ *
+ */
+
+#include <kunit/test.h>
+
+static void
+test_cmp_map(struct kunit *test, struct status_to_posix_error *expect)
+{
+	struct status_to_posix_error *result;
+
+	result = smb2_get_err_map(expect->smb2_status);
+	KUNIT_EXPECT_PTR_NE(test, NULL, result);
+	KUNIT_EXPECT_EQ(test, expect->smb2_status, result->smb2_status);
+	KUNIT_EXPECT_EQ(test, expect->posix_error, result->posix_error);
+	KUNIT_EXPECT_STREQ(test, expect->status_string, result->status_string);
+}
+
+static void maperror_test_check_search(struct kunit *test)
+{
+	unsigned int i;
+	struct status_to_posix_error expect;
+
+	for (i = 0; i < err_map_num; i++) {
+		expect = smb2_error_map_table[i];
+		test_cmp_map(test, &expect);
+	}
+}
+
+static struct kunit_case maperror_test_cases[] = {
+	KUNIT_CASE(maperror_test_check_search),
+	{}
+};
+
+static struct kunit_suite maperror_suite = {
+	.name = "smb2_maperror",
+	.test_cases = maperror_test_cases,
+};
+
+kunit_test_suite(maperror_suite);
+
+MODULE_LICENSE("GPL");
-- 
2.43.0