diff --git a/tests/driver_sdcard_spi/main.c b/tests/driver_sdcard_spi/main.c
index b0f293ad5b..4d3d1818ec 100644
--- a/tests/driver_sdcard_spi/main.c
+++ b/tests/driver_sdcard_spi/main.c
@@ -188,10 +188,9 @@ static int _size(int argc, char **argv)
 
     uint32_t gb_int = bytes / (SDCARD_SPI_SI_KILO * SDCARD_SPI_SI_KILO * SDCARD_SPI_SI_KILO);
     uint32_t gb_frac = (bytes / (SDCARD_SPI_SI_KILO * SDCARD_SPI_SI_KILO))
-                       - (gb_int * SDCARD_SPI_SI_KILO); //[MB]
+                       - (gb_int * SDCARD_SPI_SI_KILO); /* [MB] */
 
     puts("\nCard size: ");
-    //fflush(stdout);
     print_u64_dec( bytes );
     printf(" bytes (%lu,%03lu GiB | %lu,%03lu GB)\n", gib_int, gib_frac, gb_int, gb_frac);
     return 0;
diff --git a/tests/pkg_microcoap/coap.c b/tests/pkg_microcoap/coap.c
index 8e42c478c2..a5adaae1c6 100644
--- a/tests/pkg_microcoap/coap.c
+++ b/tests/pkg_microcoap/coap.c
@@ -49,7 +49,7 @@ static int handle_get_well_known_core(coap_rw_buffer_t *scratch,
     const coap_endpoint_t *ep = endpoints;
     int i;
 
-    len--; // Null-terminated string
+    len--; /* Null-terminated string */
 
     while (NULL != ep->handler) {
         if (NULL == ep->core_attr) {
diff --git a/tests/unittests/tests-ecc/tests-ecc.c b/tests/unittests/tests-ecc/tests-ecc.c
index b520c356cd..8069d3e1c2 100644
--- a/tests/unittests/tests-ecc/tests-ecc.c
+++ b/tests/unittests/tests-ecc/tests-ecc.c
@@ -41,7 +41,7 @@ static void test_single(void)
     TEST_ASSERT_EQUAL_INT(Hamming_ERROR_MULTIPLEBITS, result);
 
     memset(data, 0xAB, 256);
-    ecc[1] ^= 1; // Flip first bit, corrupting the ECC
+    ecc[1] ^= 1; /* Flip first bit, corrupting the ECC */
     result = hamming_verify256x(data, 256, ecc);
     TEST_ASSERT_EQUAL_INT(Hamming_ERROR_ECC, result);
 }
@@ -68,7 +68,7 @@ static void test_padding(void)
     TEST_ASSERT_EQUAL_INT(Hamming_ERROR_MULTIPLEBITS, result);
 
     memset(data, 0xAB, 203);
-    ecc[1] ^= 1; // Flip first bit, corrupting the ECC
+    ecc[1] ^= 1; /* Flip first bit, corrupting the ECC */
     result = hamming_verify256x(data, 203, ecc);
     TEST_ASSERT_EQUAL_INT(Hamming_ERROR_ECC, result);
 }