tests: do not use functions from extrakeys module

This fixes a bug introduced in 7d2591ce12 that
prevented compiling the library without enabling the extrakeys module.

CHANGELOG.md

@@ -10,6 +10,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 #### Added
  - Added usage example for an ElligatorSwift key exchange.
 
+#### Fixed
+- Fixed compilation when the extrakeys module is disabled.
+
 ## [0.5.0] - 2024-05-06
 
 #### Added

src/tests.c

@@ -6609,14 +6609,6 @@ static void permute(size_t *arr, size_t n) {
     }
 }
 
-static void rand_pk(secp256k1_pubkey *pk) {
-    unsigned char seckey[32];
-    secp256k1_keypair keypair;
-    testrand256(seckey);
-    CHECK(secp256k1_keypair_create(CTX, &keypair, seckey) == 1);
-    CHECK(secp256k1_keypair_pub(CTX, pk, &keypair) == 1);
-}
-
 static void test_sort_api(void) {
     secp256k1_pubkey pks[2];
     const secp256k1_pubkey *pks_ptr[2];
@@ -6624,8 +6616,8 @@ static void test_sort_api(void) {
     pks_ptr[0] = &pks[0];
     pks_ptr[1] = &pks[1];
 
-    rand_pk(&pks[0]);
-    rand_pk(&pks[1]);
+    testutil_random_pubkey_test(&pks[0]);
+    testutil_random_pubkey_test(&pks[1]);
 
     CHECK(secp256k1_ec_pubkey_sort(CTX, pks_ptr, 2) == 1);
     CHECK_ILLEGAL(CTX, secp256k1_ec_pubkey_sort(CTX, NULL, 2));
@@ -6678,7 +6670,7 @@ static void test_sort(void) {
         int j;
         const secp256k1_pubkey *pk_ptr[5];
         for (j = 0; j < 5; j++) {
-            rand_pk(&pk[j]);
+            testutil_random_pubkey_test(&pk[j]);
             pk_ptr[j] = &pk[j];
         }
         secp256k1_ec_pubkey_sort(CTX, pk_ptr, 5);

src/testutil.h

@@ -107,6 +107,12 @@ static void testutil_random_gej_test(secp256k1_gej *gej) {
     testutil_random_ge_jacobian_test(gej, &ge);
 }
 
+static void testutil_random_pubkey_test(secp256k1_pubkey *pk) {
+    secp256k1_ge ge;
+    testutil_random_ge_test(&ge);
+    secp256k1_pubkey_save(pk, &ge);
+}
+
 static void testutil_random_scalar_order_test(secp256k1_scalar *num) {
     do {
         unsigned char b32[32];