tests: Get rid of mbedtls_test_unhexify() in unit test code

In test functions calling mbedtls_test_unhexify(), change the
type of the associated parameters from `char*` to `data_t`.

That way the `unhexify` operation is done by the test
framework and not by the unit test code.

Use for the new parameters of type data_t the name of the
local variable that used to store the `unhexify` version of
the `char*` parameter.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tests/suites/test_suite_hkdf.function b/tests/suites/test_suite_hkdf.function
index 23b13d8..ddd64fa 100644
--- a/tests/suites/test_suite_hkdf.function
+++ b/tests/suites/test_suite_hkdf.function
@@ -9,43 +9,36 @@
  */
 
 /* BEGIN_CASE */
-void test_hkdf( int md_alg, char *hex_ikm_string, char *hex_salt_string,
-                char *hex_info_string, char *hex_expected_okm_string )
+void test_hkdf( int md_alg, data_t *ikm, data_t *salt, data_t *info,
+                data_t *expected_okm )
 {
     int ret;
-    size_t ikm_len, salt_len, info_len, expected_okm_len;
-    unsigned char ikm[128] = { '\0' };
-    unsigned char salt[128] = { '\0' };
-    unsigned char info[128] = { '\0' };
-    unsigned char expected_okm[128] = { '\0' };
     unsigned char okm[128] = { '\0' };
     /*
-     * okm_string is the ASCII string representation of okm,
-     * so its size is twice the size of okm, and an extra null-termination.
+     * okm_string and expected_okm_string are the ASCII string representations
+     * of km and expected_okm, so their size should be twice the size of
+     * okm and expected_okm, and an extra null-termination.
      */
     unsigned char okm_string[257] = { '\0' };
+    unsigned char expected_okm_string[257] = { '\0' };
 
     const mbedtls_md_info_t *md = mbedtls_md_info_from_type( md_alg );
     TEST_ASSERT( md != NULL );
 
-    ikm_len = mbedtls_test_unhexify( ikm, hex_ikm_string );
-    salt_len = mbedtls_test_unhexify( salt, hex_salt_string );
-    info_len = mbedtls_test_unhexify( info, hex_info_string );
-    expected_okm_len = mbedtls_test_unhexify( expected_okm,
-                                              hex_expected_okm_string );
+    TEST_ASSERT( expected_okm->len <= sizeof( okm ) );
 
-    TEST_ASSERT( expected_okm_len <= sizeof( okm ) );
-
-    ret = mbedtls_hkdf( md, salt, salt_len, ikm, ikm_len, info, info_len, okm,
-                        expected_okm_len);
+    ret = mbedtls_hkdf( md, salt->x, salt->len, ikm->x, ikm->len,
+                        info->x, info->len, okm, expected_okm->len );
     TEST_ASSERT( ret == 0 );
 
     /*
-     * Run mbedtls_test_hexify on it so that it looks nicer if the assertion
-     * fails.
+     * Run mbedtls_test_hexify on okm and expected_okm so that it looks nicer
+     * if the assertion fails.
      */
-    mbedtls_test_hexify( okm_string, okm, expected_okm_len );
-    TEST_ASSERT( !strcmp( (char *)okm_string, hex_expected_okm_string ) );
+    mbedtls_test_hexify( okm_string, okm, expected_okm->len );
+    mbedtls_test_hexify( expected_okm_string,
+                         expected_okm->x, expected_okm->len );
+    TEST_ASSERT( !strcmp( (char *)okm_string, (char *)expected_okm_string ) );
 }
 /* END_CASE */