tests: more verbosity if block decoding fails (#28814)

tests/block_test_util.go

@@ -36,6 +36,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
@@ -224,6 +225,7 @@ func (t *BlockTest) insertBlocks(blockchain *core.BlockChain) ([]btBlock, error)
 		cb, err := b.decode()
 		if err != nil {
 			if b.BlockHeader == nil {
+				log.Info("Block decoding failed", "index", bi, "err", err)
 				continue // OK - block is supposed to be invalid, continue with next block
 			} else {
 				return nil, fmt.Errorf("block RLP decoding failed when expected to succeed: %v", err)