diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index f29dcab..5441493 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -82,6 +82,63 @@
 Test mpi_write_string #10 (Negative hex with odd number of digits)
 mpi_read_write_string:16:"-1":16:"":3:0:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL
 
+Test mbedtls_mpi_core_io_be #1 (Buffer and limbs just fit, input limb-aligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":96:12:0:0
+
+Test mbedtls_mpi_core_io_be #2  (Buffer and limbs just fit, input unaligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b":94:12:0:0
+
+Test mbedtls_mpi_core_io_be #3 (Buffer just fits, extra limbs, input limb-aligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":96:14:0:0
+
+Test mbedtls_mpi_core_io_be #4 (Buffer just fits, extra limbs, input unaligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b":94:14:0:0
+
+Test mbedtls_mpi_core_io_be #5 (Extra limbs, buffer aligned to extra limbs, input limb-aligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":112:14:0:0
+
+Test mbedtls_mpi_core_io_be #6 (Extra limbs, buffer aligned to extra limbs, input unaligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b":112:14:0:0
+
+Test mbedtls_mpi_core_io_be #7 (Buffer and limbs just fit, input limb-aligned with leading zeroes)
+mbedtls_mpi_core_io_be:"00000000000000001fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":88:12:0:0
+
+Test mbedtls_mpi_core_io_be #8 (Buffer and limbs just fit, input unaligned with leading zeroes)
+mbedtls_mpi_core_io_be:"00000000000000001fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b":86:12:0:0
+
+Test mbedtls_mpi_core_io_be #9 (Buffer just fits, extra limbs, input limb-aligned with leading zeroes)
+mbedtls_mpi_core_io_be:"00000000000000001fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":88:14:0:0
+
+Test mbedtls_mpi_core_io_be #10 (Buffer just fits, extra limbs, input unaligned with leading zeroes)
+mbedtls_mpi_core_io_be:"00000000000000001fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b":86:14:0:0
+
+Test mbedtls_mpi_core_io_be #11 (Zero)
+mbedtls_mpi_core_io_be:"00":1:1:0:0
+
+Test mbedtls_mpi_core_io_be #12 (Zero, empty output)
+mbedtls_mpi_core_io_be:"00":0:1:0:0
+
+Test mbedtls_mpi_core_io_be #13 (Zero, empty input)
+mbedtls_mpi_core_io_be:"":1:1:0:0
+
+Test mbedtls_mpi_core_io_be #14 (One)
+mbedtls_mpi_core_io_be:"01":1:1:0:0
+
+Test mbedtls_mpi_core_io_be #14 (One limb)
+mbedtls_mpi_core_io_be:"ff00000000000000":8:1:0:0
+
+Test mbedtls_mpi_core_io_be #15 (not enough limbs, input limb-aligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":96:11:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL:0
+
+Test mbedtls_mpi_core_io_be #16 (not enough limbs, input unaligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b":94:11:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL:0
+
+Test mbedtls_mpi_core_io_be #17 (buffer too small, input limb-aligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":95:12:0:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL
+
+Test mbedtls_mpi_core_io_be #18 (buffer too small, input unaligned)
+mbedtls_mpi_core_io_be:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b":93:12:0:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL
+
 Base test mbedtls_mpi_read_binary #1
 mbedtls_mpi_read_binary:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"0941379D00FED1491FE15DF284DFDE4A142F68AA8D412023195CEE66883E6290FFE703F4EA5963BF212713CEE46B107C09182B5EDCD955ADAC418BF4918E2889AF48E1099D513830CEC85C26AC1E158B52620E33BA8692F893EFBB2F958B4424"
 
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 2694a44..c3e9572 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1,6 +1,7 @@
 /* BEGIN_HEADER */
 #include "mbedtls/bignum.h"
 #include "mbedtls/entropy.h"
+#include "bignum_core.h"
 
 #if MBEDTLS_MPI_MAX_BITS > 792
 #define MPI_MAX_BITS_LARGER_THAN_792
@@ -197,6 +198,67 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
+void mbedtls_mpi_core_io_be( data_t *input, int nb_int, int nx_64_int, int iret,
+                             int oret )
+{
+    #define BMAX 1024
+    unsigned char buf[BMAX];
+    #define XMAX BMAX / sizeof( mbedtls_mpi_uint )
+    mbedtls_mpi_uint X[XMAX];
+    size_t nx, nb;
+    int ret;
+
+    if( iret != 0 )
+        TEST_ASSERT( oret == 0 );
+
+    TEST_ASSERT( 0 <= nb_int );
+    nb = nb_int;
+    TEST_ASSERT( nb <= BMAX );
+
+    TEST_ASSERT( 0 <= nx_64_int );
+    nx = nx_64_int;
+    /* nx_64_int is the number of 64 bit limbs, if we have 32 bit limbs we need
+     * to double the number of limbs to have the same size. */
+    if( sizeof( mbedtls_mpi_uint ) == 4 )
+        nx *= 2;
+    TEST_ASSERT( nx <= XMAX );
+
+    ret =  mbedtls_mpi_core_read_be( X, nx, input->x, input->len );
+    TEST_ASSERT( ret == iret );
+
+    if( iret == 0 )
+    {
+        ret =  mbedtls_mpi_core_write_be( X, nx, buf, nb );
+        TEST_ASSERT( ret == oret );
+    }
+
+    if( ( iret == 0 ) && ( oret == 0 ) )
+    {
+        if( nb > input->len )
+        {
+            size_t leading_zeroes = nb - input->len;
+            TEST_ASSERT( memcmp( buf + nb - input->len, input->x, input->len ) == 0 );
+            for( size_t i = 0; i < leading_zeroes; i++ )
+                TEST_ASSERT( buf[i] == 0 );
+        }
+        else
+        {
+            size_t leading_zeroes = input->len - nb;
+            TEST_ASSERT( memcmp( input->x + input->len - nb, buf, nb ) == 0 );
+            for( size_t i = 0; i < leading_zeroes; i++ )
+                TEST_ASSERT( input->x[i] == 0 );
+        }
+    }
+
+exit:
+    ;
+
+    #undef BMAX
+    #undef XMAX
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
 void mbedtls_mpi_read_binary_le( data_t * buf, char * input_A )
 {
     mbedtls_mpi X;