diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index 8bcf766a6..e860de28c 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -109,7 +109,7 @@ const int *mbedtls_md_list( void );
  * \brief           This function returns the message-digest information
  *                  associated with the given digest name.
  *
- * \param md_name   The name of the digest to search for.
+ * \param md_name   The name of the digest to search for. This must not be \c NULL.
  *
  * \return          The message-digest information associated with \p md_name.
  * \return          NULL if the associated message-digest information is not found.
@@ -120,7 +120,7 @@ const mbedtls_md_info_t *mbedtls_md_info_from_string( const char *md_name );
  * \brief           This function returns the message-digest information
  *                  associated with the given digest type.
  *
- * \param md_type   The type of digest to search for.
+ * \param md_type   The type of digest to search for. This must not be \c NULL.
  *
  * \return          The message-digest information associated with \p md_type.
  * \return          NULL if the associated message-digest information is not found.
@@ -133,7 +133,7 @@ const mbedtls_md_info_t *mbedtls_md_info_from_type( mbedtls_md_type_t md_type );
  *
  *                  This function should always be called first. It prepares the
  *                  context for mbedtls_md_setup() for binding it to a
- *                  message-digest algorithm.
+ *                  message-digest algorithm. The \p ctx must not be \c NULL.
  */
 void mbedtls_md_init( mbedtls_md_context_t *ctx );
 
@@ -148,7 +148,7 @@ void mbedtls_md_init( mbedtls_md_context_t *ctx );
  *                  Calling this function if you have previously
  *                  called mbedtls_md_init() and nothing else is optional.
  *                  You must not call this function if you have not called
- *                  mbedtls_md_init().
+ *                  mbedtls_md_init(). The \p ctx must not be \c NULL.
  */
 void mbedtls_md_free( mbedtls_md_context_t *ctx );
 
@@ -167,7 +167,7 @@ void mbedtls_md_free( mbedtls_md_context_t *ctx );
  *
  * \deprecated      Superseded by mbedtls_md_setup() in 2.0.0
  *
- * \param ctx       The context to set up.
+ * \param ctx       The context to set up. This must not be \c NULL.
  * \param md_info   The information structure of the message-digest algorithm
  *                  to use.
  *
@@ -188,9 +188,9 @@ int mbedtls_md_init_ctx( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_
  *                  mbedtls_md_free(). Makes it necessary to call
  *                  mbedtls_md_free() later.
  *
- * \param ctx       The context to set up.
+ * \param ctx       The context to set up. This must not be \c NULL.
  * \param md_info   The information structure of the message-digest algorithm
- *                  to use.
+ *                  to use. This must not be \c NULL.
  * \param hmac      Defines if HMAC is used. 0: HMAC is not used (saves some memory),
  *                  or non-zero: HMAC is used with this context.
  *
@@ -214,8 +214,8 @@ int mbedtls_md_setup( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_inf
  * \warning         This function clones the message-digest state, not the
  *                  HMAC state.
  *
- * \param dst       The destination context.
- * \param src       The context to be cloned.
+ * \param dst       The destination context. This must not be \c NULL.
+ * \param src       The context to be cloned. This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification failure.
@@ -228,7 +228,7 @@ int mbedtls_md_clone( mbedtls_md_context_t *dst,
  *                  message-digest information structure.
  *
  * \param md_info   The information structure of the message-digest algorithm
- *                  to use.
+ *                  to use. This must not be \c NULL.
  *
  * \return          The size of the message-digest output in Bytes.
  */
@@ -239,7 +239,7 @@ unsigned char mbedtls_md_get_size( const mbedtls_md_info_t *md_info );
  *                  message-digest information structure.
  *
  * \param md_info   The information structure of the message-digest algorithm
- *                  to use.
+ *                  to use. This must not be \c NULL.
  *
  * \return          The type of the message digest.
  */
@@ -250,7 +250,7 @@ mbedtls_md_type_t mbedtls_md_get_type( const mbedtls_md_info_t *md_info );
  *                  message-digest information structure.
  *
  * \param md_info   The information structure of the message-digest algorithm
- *                  to use.
+ *                  to use. This must not be \c NULL.
  *
  * \return          The name of the message digest.
  */
@@ -280,7 +280,7 @@ int mbedtls_md_starts( mbedtls_md_context_t *ctx );
  *                  Afterwards, call mbedtls_md_finish().
  *
  * \param ctx       The generic message-digest context.
- * \param input     The buffer holding the input data.
+ * \param input     The buffer holding the input data. This must not be \c NULL.
  * \param ilen      The length of the input data.
  *
  * \return          \c 0 on success.
@@ -302,6 +302,7 @@ int mbedtls_md_update( mbedtls_md_context_t *ctx, const unsigned char *input, si
  *
  * \param ctx       The generic message-digest context.
  * \param output    The buffer for the generic message-digest checksum result.
+ *                  This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
@@ -318,10 +319,11 @@ int mbedtls_md_finish( mbedtls_md_context_t *ctx, unsigned char *output );
  *                 Output = message_digest(input buffer).
  *
  * \param md_info  The information structure of the message-digest algorithm
- *                 to use.
+ *                 to use. This must not be \c NULL.
  * \param input    The buffer holding the data.
  * \param ilen     The length of the input data.
  * \param output   The generic message-digest checksum result.
+ *                 This must not be \c NULL.
  *
  * \return         \c 0 on success.
  * \return         #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
@@ -339,9 +341,10 @@ int mbedtls_md( const mbedtls_md_info_t *md_info, const unsigned char *input, si
  *                 Output = message_digest(file contents).
  *
  * \param md_info  The information structure of the message-digest algorithm
- *                 to use.
- * \param path     The input file name.
+ *                 to use. This must not be \c NULL.
+ * \param path     The input file name. This must not be \c NULL.
  * \param output   The generic message-digest checksum result.
+ *                 This must not be \c NULL.
  *
  * \return         \c 0 on success.
  * \return         #MBEDTLS_ERR_MD_FILE_IO_ERROR on an I/O error accessing
@@ -363,7 +366,7 @@ int mbedtls_md_file( const mbedtls_md_info_t *md_info, const char *path,
  *
  * \param ctx       The message digest context containing an embedded HMAC
  *                  context.
- * \param key       The HMAC secret key.
+ * \param key       The HMAC secret key. This must not be \c NULL.
  * \param keylen    The length of the HMAC key in Bytes.
  *
  * \return          \c 0 on success.
@@ -407,7 +410,7 @@ int mbedtls_md_hmac_update( mbedtls_md_context_t *ctx, const unsigned char *inpu
  *
  * \param ctx       The message digest context containing an embedded HMAC
  *                  context.
- * \param output    The generic HMAC checksum result.
+ * \param output    The generic HMAC checksum result. This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
@@ -424,7 +427,7 @@ int mbedtls_md_hmac_finish( mbedtls_md_context_t *ctx, unsigned char *output);
  *                  input.
  *
  * \param ctx       The message digest context containing an embedded HMAC
- *                  context.
+ *                  context. This must not be \c NULL.
  *
  * \return          \c 0 on success.
  * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
@@ -443,12 +446,12 @@ int mbedtls_md_hmac_reset( mbedtls_md_context_t *ctx );
  *                 output = generic HMAC(hmac key, input buffer).
  *
  * \param md_info  The information structure of the message-digest algorithm
- *                 to use.
- * \param key      The HMAC secret key.
+ *                 to use. This must not be \c NULL.
+ * \param key      The HMAC secret key. This must not be \c NULL.
  * \param keylen   The length of the HMAC secret key in Bytes.
  * \param input    The buffer holding the input data.
  * \param ilen     The length of the input data.
- * \param output   The generic HMAC result.
+ * \param output   The generic HMAC result. This must not be \c NULL.
  *
  * \return         \c 0 on success.
  * \return         #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter-verification
diff --git a/library/md.c b/library/md.c
index 303cdcbee..821a5e81d 100644
--- a/library/md.c
+++ b/library/md.c
@@ -49,6 +49,12 @@
 #include <stdio.h>
 #endif
 
+#define MBEDTLS_MD_VALIDATE_RET(cond) \
+        MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_MD_BAD_INPUT_DATA )
+#define MBEDTLS_MD_VALIDATE_RET_NULL(cond) \
+        MBEDTLS_INTERNAL_VALIDATE_RET( cond, NULL )
+#define MBEDTLS_MD_VALIDATE(cond)    MBEDTLS_INTERNAL_VALIDATE( cond )
+
 /*
  * Reminder: update profiles in x509_crt.c when adding a new hash!
  */
@@ -94,8 +100,7 @@ const int *mbedtls_md_list( void )
 
 const mbedtls_md_info_t *mbedtls_md_info_from_string( const char *md_name )
 {
-    if( NULL == md_name )
-        return( NULL );
+    MBEDTLS_MD_VALIDATE_RET_NULL( md_name != NULL );
 
     /* Get the appropriate digest information */
 #if defined(MBEDTLS_MD2_C)
@@ -176,6 +181,7 @@ const mbedtls_md_info_t *mbedtls_md_info_from_type( mbedtls_md_type_t md_type )
 
 void mbedtls_md_init( mbedtls_md_context_t *ctx )
 {
+    MBEDTLS_MD_VALIDATE( ctx != NULL );
     memset( ctx, 0, sizeof( mbedtls_md_context_t ) );
 }
 
@@ -200,12 +206,11 @@ void mbedtls_md_free( mbedtls_md_context_t *ctx )
 int mbedtls_md_clone( mbedtls_md_context_t *dst,
                       const mbedtls_md_context_t *src )
 {
-    if( dst == NULL || dst->md_info == NULL ||
-        src == NULL || src->md_info == NULL ||
-        dst->md_info != src->md_info )
-    {
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    }
+    MBEDTLS_MD_VALIDATE_RET( dst != NULL );
+    MBEDTLS_MD_VALIDATE_RET( src != NULL );
+    MBEDTLS_MD_VALIDATE_RET( dst->md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( src->md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( dst->md_info == src->md_info );
 
     dst->md_info->clone_func( dst->md_ctx, src->md_ctx );
 
@@ -221,8 +226,8 @@ int mbedtls_md_init_ctx( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_
 
 int mbedtls_md_setup( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_info, int hmac )
 {
-    if( md_info == NULL || ctx == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
 
     if( ( ctx->md_ctx = md_info->ctx_alloc_func() ) == NULL )
         return( MBEDTLS_ERR_MD_ALLOC_FAILED );
@@ -244,24 +249,26 @@ int mbedtls_md_setup( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_inf
 
 int mbedtls_md_starts( mbedtls_md_context_t *ctx )
 {
-    if( ctx == NULL || ctx->md_info == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->md_info != NULL );
 
     return( ctx->md_info->starts_func( ctx->md_ctx ) );
 }
 
 int mbedtls_md_update( mbedtls_md_context_t *ctx, const unsigned char *input, size_t ilen )
 {
-    if( ctx == NULL || ctx->md_info == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( input != NULL );
 
     return( ctx->md_info->update_func( ctx->md_ctx, input, ilen ) );
 }
 
 int mbedtls_md_finish( mbedtls_md_context_t *ctx, unsigned char *output )
 {
-    if( ctx == NULL || ctx->md_info == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( output != NULL );
 
     return( ctx->md_info->finish_func( ctx->md_ctx, output ) );
 }
@@ -269,8 +276,8 @@ int mbedtls_md_finish( mbedtls_md_context_t *ctx, unsigned char *output )
 int mbedtls_md( const mbedtls_md_info_t *md_info, const unsigned char *input, size_t ilen,
             unsigned char *output )
 {
-    if( md_info == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( output != NULL );
 
     return( md_info->digest_func( input, ilen, output ) );
 }
@@ -284,8 +291,9 @@ int mbedtls_md_file( const mbedtls_md_info_t *md_info, const char *path, unsigne
     mbedtls_md_context_t ctx;
     unsigned char buf[1024];
 
-    if( md_info == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( path != NULL );
+    MBEDTLS_MD_VALIDATE_RET( output != NULL );
 
     if( ( f = fopen( path, "rb" ) ) == NULL )
         return( MBEDTLS_ERR_MD_FILE_IO_ERROR );
@@ -323,8 +331,10 @@ int mbedtls_md_hmac_starts( mbedtls_md_context_t *ctx, const unsigned char *key,
     unsigned char *ipad, *opad;
     size_t i;
 
-    if( ctx == NULL || ctx->md_info == NULL || ctx->hmac_ctx == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->md_info  != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->hmac_ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( key != NULL );
 
     if( keylen > (size_t) ctx->md_info->block_size )
     {
@@ -365,8 +375,9 @@ cleanup:
 
 int mbedtls_md_hmac_update( mbedtls_md_context_t *ctx, const unsigned char *input, size_t ilen )
 {
-    if( ctx == NULL || ctx->md_info == NULL || ctx->hmac_ctx == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->hmac_ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->md_info != NULL );
 
     return( ctx->md_info->update_func( ctx->md_ctx, input, ilen ) );
 }
@@ -377,8 +388,10 @@ int mbedtls_md_hmac_finish( mbedtls_md_context_t *ctx, unsigned char *output )
     unsigned char tmp[MBEDTLS_MD_MAX_SIZE];
     unsigned char *opad;
 
-    if( ctx == NULL || ctx->md_info == NULL || ctx->hmac_ctx == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->hmac_ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( output != NULL );
 
     opad = (unsigned char *) ctx->hmac_ctx + ctx->md_info->block_size;
 
@@ -400,8 +413,9 @@ int mbedtls_md_hmac_reset( mbedtls_md_context_t *ctx )
     int ret;
     unsigned char *ipad;
 
-    if( ctx == NULL || ctx->md_info == NULL || ctx->hmac_ctx == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->hmac_ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->md_info != NULL );
 
     ipad = (unsigned char *) ctx->hmac_ctx;
 
@@ -419,8 +433,9 @@ int mbedtls_md_hmac( const mbedtls_md_info_t *md_info,
     mbedtls_md_context_t ctx;
     int ret;
 
-    if( md_info == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( md_info != NULL );
+    MBEDTLS_MD_VALIDATE_RET( key != NULL );
+    MBEDTLS_MD_VALIDATE_RET( output != NULL );
 
     mbedtls_md_init( &ctx );
 
@@ -442,32 +457,29 @@ cleanup:
 
 int mbedtls_md_process( mbedtls_md_context_t *ctx, const unsigned char *data )
 {
-    if( ctx == NULL || ctx->md_info == NULL )
-        return( MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    MBEDTLS_MD_VALIDATE_RET( ctx != NULL );
+    MBEDTLS_MD_VALIDATE_RET( ctx->md_info != NULL );
 
     return( ctx->md_info->process_func( ctx->md_ctx, data ) );
 }
 
 unsigned char mbedtls_md_get_size( const mbedtls_md_info_t *md_info )
 {
-    if( md_info == NULL )
-        return( 0 );
+    MBEDTLS_INTERNAL_VALIDATE_RET( md_info != NULL, 0 );
 
     return md_info->size;
 }
 
 mbedtls_md_type_t mbedtls_md_get_type( const mbedtls_md_info_t *md_info )
 {
-    if( md_info == NULL )
-        return( MBEDTLS_MD_NONE );
+    MBEDTLS_INTERNAL_VALIDATE_RET( md_info != NULL, MBEDTLS_MD_NONE );
 
     return md_info->type;
 }
 
 const char *mbedtls_md_get_name( const mbedtls_md_info_t *md_info )
 {
-    if( md_info == NULL )
-        return( NULL );
+    MBEDTLS_MD_VALIDATE_RET_NULL( md_info != NULL );
 
     return md_info->name;
 }
diff --git a/tests/suites/test_suite_md.function b/tests/suites/test_suite_md.function
index 11cf88ae7..d72c03816 100644
--- a/tests/suites/test_suite_md.function
+++ b/tests/suites/test_suite_md.function
@@ -39,7 +39,7 @@ exit:
 }
 /* END_CASE */
 
-/* BEGIN_CASE */
+/* BEGIN_CASE depends_on:MBEDTLS_CHECK_PARAMS:!MBEDTLS_PARAM_FAILED_ALT */
 void md_null_args(  )
 {
     mbedtls_md_context_t ctx;
@@ -48,53 +48,46 @@ void md_null_args(  )
 
     mbedtls_md_init( &ctx );
 
-    TEST_ASSERT( mbedtls_md_get_size( NULL ) == 0 );
-    TEST_ASSERT( mbedtls_md_get_type( NULL ) == MBEDTLS_MD_NONE );
-    TEST_ASSERT( mbedtls_md_get_name( NULL ) == NULL );
+    TEST_INVALID_PARAM( mbedtls_md_get_size( NULL ) == 0 );
+    TEST_INVALID_PARAM( mbedtls_md_get_type( NULL ) == MBEDTLS_MD_NONE );
+    TEST_INVALID_PARAM( mbedtls_md_get_name( NULL ) == NULL );
 
-    TEST_ASSERT( mbedtls_md_info_from_string( NULL ) == NULL );
+    TEST_INVALID_PARAM( mbedtls_md_info_from_string( NULL ) == NULL );
 
-    TEST_ASSERT( mbedtls_md_setup( &ctx, NULL, 0 ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_setup( NULL, info, 0 ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_setup( &ctx, NULL, 0 ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_setup( NULL, info, 0 ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
 
-    TEST_ASSERT( mbedtls_md_starts( NULL ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_starts( &ctx ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_starts( NULL ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_starts( &ctx ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
 
-    TEST_ASSERT( mbedtls_md_update( NULL, buf, 1 ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_update( &ctx, buf, 1 ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_update( NULL, buf, 1 ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_update( &ctx, buf, 1 ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
 
-    TEST_ASSERT( mbedtls_md_finish( NULL, buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_finish( &ctx, buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_finish( NULL, buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_finish( &ctx, buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
 
-    TEST_ASSERT( mbedtls_md( NULL, buf, 1, buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md( NULL, buf, 1, buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
 
 #if defined(MBEDTLS_FS_IO)
-    TEST_ASSERT( mbedtls_md_file( NULL, "", buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_file( NULL, "", buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
 #endif
 
-    TEST_ASSERT( mbedtls_md_hmac_starts( NULL, buf, 1 )
-                 == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_hmac_starts( &ctx, buf, 1 )
-                 == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_hmac_starts( NULL, buf, 1 ) );
+    TEST_INVALID_PARAM( mbedtls_md_hmac_starts( &ctx, buf, 1 ) );
 
-    TEST_ASSERT( mbedtls_md_hmac_update( NULL, buf, 1 )
-                 == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_hmac_update( &ctx, buf, 1 )
-                 == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_hmac_update( NULL, buf, 1 ) );
+    TEST_INVALID_PARAM( mbedtls_md_hmac_update( &ctx, buf, 1 ) );
 
-    TEST_ASSERT( mbedtls_md_hmac_finish( NULL, buf )
-                 == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_hmac_finish( &ctx, buf )
-                 == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_hmac_finish( NULL, buf ) );
+    TEST_INVALID_PARAM( mbedtls_md_hmac_finish( &ctx, buf ) );
 
-    TEST_ASSERT( mbedtls_md_hmac_reset( NULL ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_hmac_reset( &ctx ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_hmac_reset( NULL ) );
+    TEST_INVALID_PARAM( mbedtls_md_hmac_reset( &ctx ) );
 
-    TEST_ASSERT( mbedtls_md_hmac( NULL, buf, 1, buf, 1, buf )
-                 == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_hmac( NULL, buf, 1, buf, 1, buf ) );
 
-    TEST_ASSERT( mbedtls_md_process( NULL, buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
-    TEST_ASSERT( mbedtls_md_process( &ctx, buf ) == MBEDTLS_ERR_MD_BAD_INPUT_DATA );
+    TEST_INVALID_PARAM( mbedtls_md_process( NULL, buf ) );
+    TEST_INVALID_PARAM( mbedtls_md_process( &ctx, buf ) );
 
     /* Ok, this is not NULL arg but NULL return... */
     TEST_ASSERT( mbedtls_md_info_from_type( MBEDTLS_MD_NONE ) == NULL );