op-node/rollup/derive/test: Add RandomL2Block

Also adds a function RandomBlockPrependTxs to package op-node/testutils
to avoid code duplication with RandomBlock.

op-node/rollup/derive/test/random.go

+package test
+
+import (
+	"math/rand"
+
+	"github.com/ethereum-optimism/optimism/op-node/eth"
+	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
+	"github.com/ethereum-optimism/optimism/op-node/testutils"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+// RandomL2Block returns a random block whose first transaction is a random
+// L1 Info Deposit transaction.
+func RandomL2Block(rng *rand.Rand, txCount int) (*types.Block, []*types.Receipt) {
+	l1Block := types.NewBlock(testutils.RandomHeader(rng),
+		nil, nil, nil, trie.NewStackTrie(nil))
+	l1InfoTx, err := derive.L1InfoDeposit(0, l1Block, eth.SystemConfig{}, testutils.RandomBool(rng))
+	if err != nil {
+		panic("L1InfoDeposit: " + err.Error())
+	}
+	return testutils.RandomBlockPrependTxs(rng, txCount, types.NewTx(l1InfoTx))
+}

op-node/testutils/random.go

@@ -206,13 +206,21 @@ func RandomHeader(rng *rand.Rand) *types.Header {
 }
 
 func RandomBlock(rng *rand.Rand, txCount uint64) (*types.Block, []*types.Receipt) {
+	return RandomBlockPrependTxs(rng, int(txCount))
+}
+
+// RandomBlockPrependTxs returns a random block with txCount randomly generated
+// transactions and additionally the transactions ptxs prepended. So the total
+// number of transactions is len(ptxs) + txCount.
+func RandomBlockPrependTxs(rng *rand.Rand, txCount int, ptxs ...*types.Transaction) (*types.Block, []*types.Receipt) {
 	header := RandomHeader(rng)
 	signer := types.NewLondonSigner(big.NewInt(rng.Int63n(1000)))
-	txs := make([]*types.Transaction, 0, txCount)
-	for i := uint64(0); i < txCount; i++ {
+	txs := make([]*types.Transaction, 0, txCount+len(ptxs))
+	txs = append(txs, ptxs...)
+	for i := 0; i < txCount; i++ {
 		txs = append(txs, RandomTx(rng, header.BaseFee, signer))
 	}
-	receipts := make([]*types.Receipt, 0, txCount)
+	receipts := make([]*types.Receipt, 0, len(txs))
 	cumulativeGasUsed := uint64(0)
 	for i, tx := range txs {
 		r := RandomReceipt(rng, signer, tx, uint64(i), cumulativeGasUsed)