diff --git a/library/cipher.c b/library/cipher.c
index b62f1d5..409c3fe 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -527,6 +527,10 @@
 
     *olen = 0;
     block_size = mbedtls_cipher_get_block_size( ctx );
+    if ( 0 == block_size )
+    {
+        return( MBEDTLS_ERR_CIPHER_INVALID_CONTEXT );
+    }
 
     if( ctx->cipher_info->mode == MBEDTLS_MODE_ECB )
     {
@@ -562,11 +566,6 @@
     }
 #endif
 
-    if ( 0 == block_size )
-    {
-        return( MBEDTLS_ERR_CIPHER_INVALID_CONTEXT );
-    }
-
     if( input == output &&
        ( ctx->unprocessed_len != 0 || ilen % block_size ) )
     {
@@ -625,11 +624,6 @@
          */
         if( 0 != ilen )
         {
-            if( 0 == block_size )
-            {
-                return( MBEDTLS_ERR_CIPHER_INVALID_CONTEXT );
-            }
-
             /* Encryption: only cache partial blocks
              * Decryption w/ padding: always keep at least one whole block
              * Decryption w/o padding: only cache partial blocks
diff --git a/tests/suites/helpers.function b/tests/suites/helpers.function
index 0cce463..3e68c06 100644
--- a/tests/suites/helpers.function
+++ b/tests/suites/helpers.function
@@ -158,11 +158,10 @@
     }                                                             \
     while( 0 )
 
-/** Allocate memory dynamically. Exit the test if this fails, but do
- * not mark the test as failed.
+/** Allocate memory dynamically. If the allocation fails, skip the test case.
  *
  * This macro behaves like #ASSERT_ALLOC, except that if the allocation
- * fails, it jumps to the \c exit label without calling test_fail().
+ * fails, it marks the test as skipped rather than failed.
  */
 #define ASSERT_ALLOC_WEAK( pointer, length )                      \
     do                                                            \
@@ -172,8 +171,7 @@
         {                                                         \
             ( pointer ) = mbedtls_calloc( sizeof( *( pointer ) ), \
                                           ( length ) );           \
-            if( ( pointer ) == NULL )                             \
-                goto exit;                                        \
+            TEST_ASSUME( ( pointer ) != NULL );                   \
         }                                                         \
     }                                                             \
     while( 0 )
diff --git a/tests/suites/test_suite_asn1parse.function b/tests/suites/test_suite_asn1parse.function
index d747cc2..f07fd40 100644
--- a/tests/suites/test_suite_asn1parse.function
+++ b/tests/suites/test_suite_asn1parse.function
@@ -121,6 +121,7 @@
 {
     unsigned char *buf = NULL;
     unsigned char *p = NULL;
+    unsigned char *end;
     size_t parsed_length;
     int ret;
 
@@ -130,7 +131,8 @@
     if( buffer_size == 0 )
     {
         ASSERT_ALLOC( buf, 1 );
-        p = buf + 1;
+        end = buf + 1;
+        p = end;
     }
     else
     {
@@ -145,9 +147,10 @@
             memcpy( buf, input->x, buffer_size );
         }
         p = buf;
+        end = buf + buffer_size;
     }
 
-    ret = mbedtls_asn1_get_len( &p, buf + buffer_size, &parsed_length );
+    ret = mbedtls_asn1_get_len( &p, end, &parsed_length );
 
     if( buffer_size >= input->len + actual_length )
     {
diff --git a/tests/suites/test_suite_ecdsa.function b/tests/suites/test_suite_ecdsa.function
index ab3db3a..59c1c49 100644
--- a/tests/suites/test_suite_ecdsa.function
+++ b/tests/suites/test_suite_ecdsa.function
@@ -500,7 +500,9 @@
     TEST_ASSERT( md_info != NULL );
 
     hlen = mbedtls_md_get_size( md_info );
-    mbedtls_md( md_info, (const unsigned char *) msg, strlen( msg ), hash );
+    TEST_ASSERT( mbedtls_md( md_info,
+                             (const unsigned char *) msg, strlen( msg ),
+                             hash ) == 0 );
 
     mbedtls_ecp_set_max_ops( max_ops );
 
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 63a2509..0f35a2a 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -600,8 +600,8 @@
     TEST_ASSERT( mbedtls_mpi_read_string( &X, 16, input_X ) == 0 );
     TEST_ASSERT( mbedtls_mpi_read_string( &Y, 16, input_Y ) == 0 );
 
-    mbedtls_mpi_grow( &X, size_X );
-    mbedtls_mpi_grow( &Y, size_Y );
+    TEST_ASSERT( mbedtls_mpi_grow( &X, size_X ) == 0 );
+    TEST_ASSERT( mbedtls_mpi_grow( &Y, size_Y ) == 0 );
 
     TEST_ASSERT( mbedtls_mpi_lt_mpi_ct( &X, &Y, &ret ) == input_err );
     if( input_err == 0 )
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index 926cec4..4742725 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -844,7 +844,9 @@
     TEST_ASSERT( md_info != NULL );
 
     hlen = mbedtls_md_get_size( md_info );
-    mbedtls_md( md_info, (const unsigned char *) msg, strlen( msg ), hash );
+    TEST_ASSERT( mbedtls_md( md_info,
+                             (const unsigned char *) msg, strlen( msg ),
+                             hash ) == 0 );
 
     mbedtls_ecp_set_max_ops( max_ops );