diff --git a/tests/suites/test_suite_gcm.function b/tests/suites/test_suite_gcm.function
index 9b7b0ee..c2f3534 100644
--- a/tests/suites/test_suite_gcm.function
+++ b/tests/suites/test_suite_gcm.function
@@ -1,5 +1,57 @@
 /* BEGIN_HEADER */
 #include "mbedtls/gcm.h"
+
+/* Use the multipart interface to process the encrypted data in two parts
+ * and check that the output matches the expected output.
+ * The context must have been set up with the key. */
+static int check_multipart( mbedtls_gcm_context *ctx,
+                            int mode,
+                            const data_t *iv,
+                            const data_t *add,
+                            const data_t *input,
+                            const data_t *expected_output,
+                            const data_t *tag,
+                            size_t n1 )
+{
+    int ok = 0;
+    uint8_t *output = NULL;
+    size_t n2 = input->len - n1;
+
+    /* Sanity checks on the test data */
+    TEST_ASSERT( n1 <= input->len );
+    TEST_EQUAL( input->len, expected_output->len );
+
+    TEST_EQUAL( 0, mbedtls_gcm_starts( ctx, mode,
+                                         iv->x, iv->len,
+                                         add->x, add->len ) );
+
+    /* Allocate a tight buffer for each update call. This way, if the function
+     * tries to write beyond the advertised required buffer size, this will
+     * count as an overflow for memory sanitizers and static checkers. */
+    ASSERT_ALLOC( output, n1 );
+    TEST_EQUAL( 0, mbedtls_gcm_update( ctx, n1, input->x, output ) );
+    ASSERT_COMPARE( output, n1, expected_output->x, n1 );
+    mbedtls_free( output );
+    output = NULL;
+
+    ASSERT_ALLOC( output, n2 );
+    TEST_EQUAL( 0, mbedtls_gcm_update( ctx, n2, input->x + n1, output ) );
+    ASSERT_COMPARE( output, n2, expected_output->x + n1, n2 );
+    mbedtls_free( output );
+    output = NULL;
+
+    ASSERT_ALLOC( output, tag->len );
+    TEST_EQUAL( 0, mbedtls_gcm_finish( ctx, output, tag->len ) );
+    ASSERT_COMPARE( output, tag->len, tag->x, tag->len );
+    mbedtls_free( output );
+    output = NULL;
+
+    ok = 1;
+exit:
+    mbedtls_free( output );
+    return( ok );
+}
+
 /* END_HEADER */
 
 /* BEGIN_DEPENDENCIES
@@ -43,6 +95,7 @@
     unsigned char tag_output[16];
     mbedtls_gcm_context ctx;
     size_t tag_len = tag_len_bits / 8;
+    size_t n1;
 
     mbedtls_gcm_init( &ctx );
 
@@ -55,10 +108,18 @@
     {
         TEST_ASSERT( mbedtls_gcm_crypt_and_tag( &ctx, MBEDTLS_GCM_ENCRYPT, src_str->len, iv_str->x, iv_str->len, add_str->x, add_str->len, src_str->x, output, tag_len, tag_output ) == 0 );
 
-        TEST_ASSERT( mbedtls_test_hexcmp( output, dst->x,
-                                          src_str->len, dst->len ) == 0 );
-        TEST_ASSERT( mbedtls_test_hexcmp( tag_output, tag->x,
-                                          tag_len, tag->len ) == 0 );
+        ASSERT_COMPARE( output, src_str->len, dst->x, dst->len );
+        ASSERT_COMPARE( tag_output, tag_len, tag->x, tag->len );
+
+        for( n1 = 16; n1 < src_str->len; n1 += 16 )
+        {
+            mbedtls_test_set_step( n1 );
+            if( !check_multipart( &ctx, MBEDTLS_GCM_ENCRYPT,
+                                  iv_str, add_str, src_str,
+                                  dst, tag,
+                                  n1 ) )
+                goto exit;
+        }
     }
 
 exit:
@@ -77,6 +138,7 @@
     mbedtls_gcm_context ctx;
     int ret;
     size_t tag_len = tag_len_bits / 8;
+    size_t n1;
 
     mbedtls_gcm_init( &ctx );
 
@@ -95,10 +157,17 @@
         else
         {
             TEST_ASSERT( ret == 0 );
+            ASSERT_COMPARE( output, src_str->len, pt_result->x, pt_result->len );
 
-            TEST_ASSERT( mbedtls_test_hexcmp( output, pt_result->x,
-                                              src_str->len,
-                                              pt_result->len ) == 0 );
+            for( n1 = 16; n1 < src_str->len; n1 += 16 )
+            {
+                mbedtls_test_set_step( n1 );
+                if( !check_multipart( &ctx, MBEDTLS_GCM_DECRYPT,
+                                      iv_str, add_str, src_str,
+                                      pt_result, tag_str,
+                                      n1 ) )
+                    goto exit;
+            }
         }
     }