Add test for wolfSSL_use_AltPrivateKey_Id to verify successful key ID allocation

tests/api.c

@@ -1696,6 +1696,38 @@ static int test_dual_alg_ecdsa_mldsa(void)
     return EXPECT_RESULT();
 }
 
+/* Test wolfSSL_use_AltPrivateKey_Id.
+ * Verify that a valid key ID can be set successfully. Guards against an
+ * inverted AllocDer return check (== 0 vs != 0) that would treat successful
+ * allocation as failure. */
+static int test_wolfSSL_use_AltPrivateKey_Id(void)
+{
+    EXPECT_DECLS;
+#if defined(WOLFSSL_DUAL_ALG_CERTS) && !defined(NO_TLS) && \
+    !defined(NO_WOLFSSL_CLIENT)
+    WOLFSSL_CTX* ctx = NULL;
+    WOLFSSL*     ssl = NULL;
+    const unsigned char id[] = { 0x01, 0x02, 0x03, 0x04 };
+
+    ExpectNotNull(ctx = wolfSSL_CTX_new(wolfSSLv23_client_method()));
+    ExpectNotNull(ssl = wolfSSL_new(ctx));
+
+    /* Negative tests. */
+    ExpectIntEQ(wolfSSL_use_AltPrivateKey_Id(NULL, id, sizeof(id),
+        INVALID_DEVID), 0);
+    ExpectIntEQ(wolfSSL_use_AltPrivateKey_Id(ssl, NULL, sizeof(id),
+        INVALID_DEVID), 0);
+
+    /* Positive test — valid ID should succeed. */
+    ExpectIntEQ(wolfSSL_use_AltPrivateKey_Id(ssl, id, sizeof(id),
+        INVALID_DEVID), 1);
+
+    wolfSSL_free(ssl);
+    wolfSSL_CTX_free(ctx);
+#endif /* WOLFSSL_DUAL_ALG_CERTS && !NO_TLS && !NO_WOLFSSL_CLIENT */
+    return EXPECT_RESULT();
+}
+
 
 /*----------------------------------------------------------------------------*
  | Context
@@ -35313,6 +35345,8 @@ TEST_CASE testCases[] = {
 
     TEST_DECL(test_dual_alg_ecdsa_mldsa),
 
+    TEST_DECL(test_wolfSSL_use_AltPrivateKey_Id),
+
     /*********************************
      * OpenSSL compatibility API tests
      *********************************/