fix(consume): consume sync validation relies on FCU only (#1670)

Author: fselmo

docs/CHANGELOG.md

@@ -14,12 +14,14 @@ Test fixtures for use by clients are available for each release on the [Github r
 
 #### `consume`
 
+- 🐞 Fix a bug with `consume sync` tests where some clients don't have JSON-RPC immediately available after syncing and can't yet serve the synced block ([#1670](https://github.com/ethereum/execution-specs/pull/1670)).
+
 ### 📋 Misc
 
 ### 🧪 Test Cases
 
-- 🐞Fix BALs opcode OOG test vectors by updating the Amsterdam commit hash in specs and validating appropriately on the testing side ([#2293](https://github.com/ethereum/execution-spec-tests/pull/2293)).
-- ✨Fix test vector for BALs SSTORE with OOG by pointing to updated specs; add new boundary conditions cases for SSTORE w/ OOG ([#2297](https://github.com/ethereum/execution-spec-tests/pull/2297)).
+- 🐞 Fix BALs opcode OOG test vectors by updating the Amsterdam commit hash in specs and validating appropriately on the testing side ([#2293](https://github.com/ethereum/execution-spec-tests/pull/2293)).
+- ✨ Fix test vector for BALs SSTORE with OOG by pointing to updated specs; add new boundary conditions cases for SSTORE w/ OOG ([#2297](https://github.com/ethereum/execution-spec-tests/pull/2297)).
 
 ## [v5.3.0](https://github.com/ethereum/execution-spec-tests/releases/tag/v5.3.0) - 2025-10-09
 

docs/running_tests/test_formats/blockchain_test_sync.md

@@ -48,9 +48,8 @@ For each [`HiveFixture`](#hivefixture) test object in the JSON fixture file, per
     - Send `engine_forkchoiceUpdatedVX` pointing to the last block hash
 
 4. Monitor and verify synchronization:
-    - Wait for the sync client to reach the [`lastblockhash`](#-lastblockhash-hash)
-    - Verify the final state root matches between both clients
-    - If [`post`](#-post-alloc) is provided, verify the final state matches
+    - Wait for the sync client to return `VALID` for `engine_forkchoiceUpdatedVX` with the sync block payload
+    - If RPC is available after sync, retrieve the sync block via `eth_getBlockByHash` for [`lastblockhash`](#-lastblockhash-hash) and check the state root matches on this block for client under test and sync client
 
 ## Structures
 

packages/testing/src/execution_testing/cli/pytest_commands/plugins/consume/simulators/simulator_logic/test_via_sync.py

@@ -503,44 +503,73 @@ def test_blockchain_via_sync(
                 f"within timeout"
             )
 
-        logger.info("Sync verification successful!")
+        logger.info("Sync verification successful! FCU returned VALID.")
 
         # Verify the final state but give a few tries
         assert eth_rpc is not None, "eth_rpc is required"
         assert sync_eth_rpc is not None, "sync_eth_rpc is required"
 
-        for attempt in range(5):
+        max_attempts = 5  # 5 attempts with 1 second wait between
+        for attempt in range(max_attempts):
             try:
                 sync_block = sync_eth_rpc.get_block_by_hash(
                     last_valid_block_hash
                 )
                 client_block = eth_rpc.get_block_by_hash(last_valid_block_hash)
 
-                if sync_block is None or client_block is None:
-                    raise LoggedError(
-                        f"Failed to retrieve block {last_valid_block_hash} "
-                        f"on attempt {attempt + 1}"
-                    )
+                if sync_block is not None and client_block is not None:
+                    # If we have both blocks, verify they match
+                    if sync_block["stateRoot"] != client_block["stateRoot"]:
+                        raise LoggedError(
+                            f"State root mismatch after sync. "
+                            f"Sync client: {sync_block['stateRoot']}, "
+                            f"Client under test: {client_block['stateRoot']}"
+                        )
 
-                if sync_block["stateRoot"] != client_block["stateRoot"]:
-                    raise LoggedError(
-                        f"State root mismatch after sync. "
-                        f"Sync client: {sync_block['stateRoot']}, "
-                        f"Client under test: {client_block['stateRoot']}"
-                    )
+                    if fixture.post_state_hash:
+                        if sync_block["stateRoot"] != str(
+                            fixture.post_state_hash
+                        ):
+                            raise LoggedError(
+                                f"Final state root mismatch. "
+                                f"Expected: {fixture.post_state_hash}, "
+                                f"Got: {sync_block['stateRoot']}"
+                            )
 
-                if fixture.post_state_hash:
-                    if sync_block["stateRoot"] != str(fixture.post_state_hash):
-                        raise LoggedError(
-                            f"Final state root mismatch. "
-                            f"Expected: {fixture.post_state_hash}, "
-                            f"Got: {sync_block['stateRoot']}"
+                    logger.info(
+                        f"Block state verified via eth_getBlockByHash (attempt {attempt + 1}): "
+                        f"{sync_block['stateRoot']}"
+                    )
+                    break
+                else:
+                    missing = []
+                    if sync_block is None:
+                        missing.append("sync_client")
+                    if client_block is None:
+                        missing.append("client_under_test")
+
+                    if attempt < max_attempts - 1:
+                        logger.debug(
+                            f"Block {last_valid_block_hash} not yet available on {', '.join(missing)} "
+                            f"(attempt {attempt + 1}/{max_attempts})"
                         )
-                break
+                        time.sleep(1)
+                    else:
+                        # Final attempt and blocks still not available
+                        logger.debug(
+                            f"Block {last_valid_block_hash} not available via eth_getBlockByHash "
+                            f"after {max_attempts} attempts (missing from: {', '.join(missing)}). "
+                            f"This is acceptable as FCU VALID is the authoritative success signal."
+                        )
+            except LoggedError:
+                # Re-raise validation errors immediately with no retry
+                raise
             except Exception as e:
-                if attempt < 4:
+                # Log other errors without failing the test
+                logger.debug(
+                    f"Error fetching blocks for verification (attempt {attempt + 1}): {e}"
+                )
+                if attempt < max_attempts - 1:
                     time.sleep(1)
-                    continue
-                raise e
 
     logger.info("Sync test completed successfully!")

packages/testing/src/execution_testing/cli/pytest_commands/plugins/consume/simulators/sync/conftest.py

@@ -55,6 +55,8 @@ def pytest_collection_modifyitems(
 
     for item in items:
         # Auto-mark all verify_sync tests as flaky with 3 reruns
+        # TODO: We can likely remove this as we have more stable sync
+        #  tests now. Leaving this here for now to be safe.
         if item.get_closest_marker("blockchain_test_sync"):
             item.add_marker(pytest.mark.flaky(reruns=3))