tests: pk_helpers: optimize failure reporting in mbedtls_pk_helpers_populate_context

Keep TEST_EQUAL() on the function that might fail so that if a failure
happen the message will report the actual function that failed.

Documentation of the helper function is also updated.

Signed-off-by: Valerio Setti <vsetti@baylibre.com>

tests/include/test/pk_helpers.h

@@ -74,7 +74,9 @@ mbedtls_svc_key_id_t mbedtls_pk_helpers_make_psa_key_from_predefined(psa_key_typ
  * \param method The desired method for populating the PK context. See
  *               "pk_context_populate_method_t" for available options.
  *
- * \return       0 on success; an error code otherwise.
+ * \return       0 on success.
+ *               In case of failure -1 is returned and the test case is marked
+ *               as failed.
  */
 int mbedtls_pk_helpers_populate_context(mbedtls_pk_context *pk, mbedtls_svc_key_id_t key_id,
                                          pk_context_populate_method_t method);

tests/src/pk_helpers.c

@@ -109,23 +109,23 @@ exit:
 int mbedtls_pk_helpers_populate_context(mbedtls_pk_context *pk, mbedtls_svc_key_id_t key_id,
                                          pk_context_populate_method_t method)
 {
-    int ret;
+    int ret = -1;
 
     switch (method) {
         case TEST_PK_WRAP_PSA:
-            ret = mbedtls_pk_wrap_psa(pk, key_id);
+            TEST_EQUAL(mbedtls_pk_wrap_psa(pk, key_id), 0);
             break;
         case TEST_PK_COPY_FROM_PSA:
-            ret = mbedtls_pk_copy_from_psa(key_id, pk);
+            TEST_EQUAL(mbedtls_pk_copy_from_psa(key_id, pk), 0);
             break;
         case TEST_PK_COPY_PUBLIC_FROM_PSA:
-            ret = mbedtls_pk_copy_public_from_psa(key_id, pk);
+            TEST_EQUAL(mbedtls_pk_copy_public_from_psa(key_id, pk), 0);
             break;
         default:
-            ret = MBEDTLS_ERR_PK_BAD_INPUT_DATA;
+            TEST_FAIL("Unknown population method");
     }
 
-    TEST_EQUAL(ret, 0);
+    ret = 0;
 
 exit:
     return ret;