diff --git a/tests/unittests/tests-crypto/tests-crypto-sha256.c b/tests/unittests/tests-crypto/tests-crypto-sha256.c
index 8f772e87af..4306b8cd90 100644
--- a/tests/unittests/tests-crypto/tests-crypto-sha256.c
+++ b/tests/unittests/tests-crypto/tests-crypto-sha256.c
@@ -10,6 +10,7 @@
 #include <limits.h>
 #include <string.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 #include "embUnit/embUnit.h"
 
@@ -17,48 +18,77 @@
 
 #include "tests-crypto.h"
 
+static int compare_str_vs_digest(const char *str,
+                                 const unsigned char hash[SHA256_DIGEST_LENGTH])
+{
+    char ch[3] = { 0, 0, 0 };
+    size_t iter_hash = 0;
+    size_t str_length = strlen(str);
+    for (size_t i = 0; i < str_length; i += 2) {
+        ch[0] = str[i];
+        ch[1] = str[i + 1];
+
+        if (hash[iter_hash++] != strtol(ch, NULL, 16)) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
 static int calc_and_compare_hash(const char *str, const char *expected)
 {
     static unsigned char hash[SHA256_DIGEST_LENGTH];
     sha256_context_t sha256;
+
     sha256_init(&sha256);
     sha256_update(&sha256, str, strlen(str));
     sha256_final(hash, &sha256);
 
-    return strncmp((const char *) hash, expected, SHA256_DIGEST_LENGTH);
+    return compare_str_vs_digest(expected, hash);
 }
 
 static void test_crypto_sha256_hash_sequence(void)
 {
     TEST_ASSERT(calc_and_compare_hash("1234567890_1",
-                 "3eda9ffe5537a588f54d0b2a453e5fa932986d0bc0f9556924f5c2379b2c91b0"));
+                                      "3eda9ffe5537a588f54d0b2a453e5fa932986d0bc0f9556924f5c2379b2c91b0"));
     TEST_ASSERT(calc_and_compare_hash("1234567890_2",
-                 "a144d0b4d285260ebbbab6840baceaa09eab3e157443c9458de764b7262c8ace"));
+                                      "a144d0b4d285260ebbbab6840baceaa09eab3e157443c9458de764b7262c8ace"));
     TEST_ASSERT(calc_and_compare_hash("1234567890_3",
-                 "9f839169d293276d1b799707d2171ac1fd5b78d0f3bc7693dbed831524dd2d77"));
+                                      "9f839169d293276d1b799707d2171ac1fd5b78d0f3bc7693dbed831524dd2d77"));
     TEST_ASSERT(calc_and_compare_hash("1234567890_4",
-                 "6c5fe2a8e3de58a5e5ac061031a8e802ae1fb9e7197862ec1aedf236f0e23475"));
+                                      "6c5fe2a8e3de58a5e5ac061031a8e802ae1fb9e7197862ec1aedf236f0e23475"));
     TEST_ASSERT(calc_and_compare_hash(
-                 "0123456789abcde-0123456789abcde-0123456789abcde-0123456789abcde-",
-                 "945ab9d52b069923680c2c067fa6092cbbd9234cf7a38628f3033b2d54d3d3bf"));
+                    "0123456789abcde-0123456789abcde-0123456789abcde-0123456789abcde-",
+                    "945ab9d52b069923680c2c067fa6092cbbd9234cf7a38628f3033b2d54d3d3bf"));
     TEST_ASSERT(calc_and_compare_hash(
-                 "Franz jagt im komplett verwahrlosten Taxi quer durch Bayern",
-                 "d32b568cd1b96d459e7291ebf4b25d007f275c9f13149beeb782fac0716613f8"));
+                    "Franz jagt im komplett verwahrlosten Taxi quer durch Bayern",
+                    "d32b568cd1b96d459e7291ebf4b25d007f275c9f13149beeb782fac0716613f8"));
     TEST_ASSERT(calc_and_compare_hash(
-                 "Frank jagt im komplett verwahrlosten Taxi quer durch Bayern",
-                 "78206a866dbb2bf017d8e34274aed01a8ce405b69d45db30bafa00f5eeed7d5e"));
+                    "Frank jagt im komplett verwahrlosten Taxi quer durch Bayern",
+                    "78206a866dbb2bf017d8e34274aed01a8ce405b69d45db30bafa00f5eeed7d5e"));
     TEST_ASSERT(calc_and_compare_hash("",
-                 "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"));
+                                      "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"));
+    TEST_ASSERT(calc_and_compare_hash(
+                    "RIOT is an open-source microkernel-based operating system, designed"
+                    " to match the requirements of Internet of Things (IoT) devices and"
+                    " other embedded devices. These requirements include a very low memory"
+                    " footprint (on the order of a few kilobytes), high energy efficiency"
+                    ", real-time capabilities, communication stacks for both wireless and"
+                    " wired networks, and support for a wide range of low-power hardware.",
+                    "06c84971e2831c48b8293144c762e3236a78217354896185b14a3a84f7cd8066"));
+    /* test failing sha256 by switching last byte of expected hash from 3b to 3c */
+    TEST_ASSERT(!calc_and_compare_hash("This test fails!",
+                                      "c19d3bf8588897076873f1a0a106ba840ca46bd1179d592953acecc4df59593c"));
 }
 
 Test *tests_crypto_sha256_tests(void)
 {
     EMB_UNIT_TESTFIXTURES(fixtures) {
-    new_TestFixture(test_crypto_sha256_hash_sequence),
-};
+        new_TestFixture(test_crypto_sha256_hash_sequence),
+    };
 
-EMB_UNIT_TESTCALLER(crypto_sha256_tests, NULL, NULL,
-        fixtures);
+    EMB_UNIT_TESTCALLER(crypto_sha256_tests, NULL, NULL,
+                        fixtures);
 
-return (Test *)&crypto_sha256_tests;
+    return (Test *)&crypto_sha256_tests;
 }