test: assumeutxo file with unknown block hash

test/functional/feature_assumeutxo.py

@@ -20,7 +20,6 @@
 - TODO: An invalid hash
 - TODO: Valid hash but invalid snapshot file (bad coin height or truncated file or
       bad other serialization)
-- TODO: Valid snapshot file, but referencing an unknown block
 - TODO: Valid snapshot file, but referencing a snapshot block that turns out to be
       invalid, or has an invalid parent
 - TODO: Valid snapshot file and snapshot block, but the block is not on the
@@ -80,6 +79,14 @@ def test_invalid_snapshot_scenarios(self, valid_snapshot_path):
         error_details = f"assumeutxo block hash in snapshot metadata not recognized ({bad_snapshot_block_hash})"
         assert_raises_rpc_error(-32603, f"Unable to load UTXO snapshot, {error_details}", self.nodes[1].loadtxoutset, bad_snapshot_path)
 
+        self.log.info("  - snapshot file refering to a block that is unknown")
+        # Represents any unknown block hash
+        bogus_block_hash = "0" * 64
+        with open(bad_snapshot_path, 'wb') as f:
+            f.write(bytes.fromhex(bogus_block_hash)[::-1] + valid_snapshot_contents[32:])
+        error_details = f"assumeutxo block hash in snapshot metadata not recognized ({bogus_block_hash})"
+        assert_raises_rpc_error(-32603, f"Unable to load UTXO snapshot, {error_details}", self.nodes[1].loadtxoutset, bad_snapshot_path)
+
         self.log.info("  - snapshot file with wrong number of coins")
         valid_num_coins = struct.unpack("<I", valid_snapshot_contents[32:32 + 4])[0]
         for off in [-1, +1]: