diff --git a/lib/test-string_helpers.c b/lib/test-string_helpers.c
index 25b5cbf..10360d4 100644
--- a/lib/test-string_helpers.c
+++ b/lib/test-string_helpers.c
@@ -238,6 +238,28 @@
 	/* terminator */
 }};
 
+static const struct test_string strings_upper[] __initconst = {
+	{
+		.in = "abcdefgh1234567890test",
+		.out = "ABCDEFGH1234567890TEST",
+	},
+	{
+		.in = "abCdeFgH1234567890TesT",
+		.out = "ABCDEFGH1234567890TEST",
+	},
+};
+
+static const struct test_string strings_lower[] __initconst = {
+	{
+		.in = "ABCDEFGH1234567890TEST",
+		.out = "abcdefgh1234567890test",
+	},
+	{
+		.in = "abCdeFgH1234567890TesT",
+		.out = "abcdefgh1234567890test",
+	},
+};
+
 static __init const char *test_string_find_match(const struct test_string_2 *s2,
 						 unsigned int flags)
 {
@@ -390,6 +412,48 @@
 	test_string_get_size_one(4096, U64_MAX, "75.6 ZB", "64.0 ZiB");
 }
 
+static void __init test_string_upper_lower(void)
+{
+	char *dst;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(strings_upper); i++) {
+		const char *s = strings_upper[i].in;
+		int len = strlen(strings_upper[i].in) + 1;
+
+		dst = kmalloc(len, GFP_KERNEL);
+		if (!dst)
+			return;
+
+		string_upper(dst, s);
+		if (memcmp(dst, strings_upper[i].out, len)) {
+			pr_warn("Test 'string_upper' failed : expected %s, got %s!\n",
+				strings_upper[i].out, dst);
+			kfree(dst);
+			return;
+		}
+		kfree(dst);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(strings_lower); i++) {
+		const char *s = strings_lower[i].in;
+		int len = strlen(strings_lower[i].in) + 1;
+
+		dst = kmalloc(len, GFP_KERNEL);
+		if (!dst)
+			return;
+
+		string_lower(dst, s);
+		if (memcmp(dst, strings_lower[i].out, len)) {
+			pr_warn("Test 'string_lower failed : : expected %s, got %s!\n",
+				strings_lower[i].out, dst);
+			kfree(dst);
+			return;
+		}
+		kfree(dst);
+	}
+}
+
 static int __init test_string_helpers_init(void)
 {
 	unsigned int i;
@@ -411,6 +475,9 @@
 	/* Test string_get_size() */
 	test_string_get_size();
 
+	/* Test string upper(), string_lower() */
+	test_string_upper_lower();
+
 	return -EINVAL;
 }
 module_init(test_string_helpers_init);