eth/tracers: refactor transaction creation and improve bad block setup

This commit refactors the transaction creation logic in `createTestTransactions` to use a range loop for better readability. It also updates the bad block setup to use the latest parent block's properties consistently. Additionally, it removes unused functions and comments to clean up the code.

Signed-off-by: katsumata <12413150+winor30@users.noreply.github.com>

Author: winor30

eth/tracers/api_test.go

@@ -1346,7 +1346,7 @@ func createTestTransactions(t *testing.T, count int) []*types.Transaction {
 	)
 
 	var transactions []*types.Transaction
-	for i := 0; i < count; i++ {
+	for i := range count {
 		tx, _ := types.SignTx(types.NewTx(&types.LegacyTx{
 			Nonce:    uint64(i),
 			To:       &testAddr,
@@ -1361,27 +1361,6 @@ func createTestTransactions(t *testing.T, count int) []*types.Transaction {
 	return transactions
 }
 
-// createSingleTransaction creates a single transaction for testing
-func createSingleTransaction(t *testing.T, nonce uint64, value *big.Int, gasLimit uint64, data []byte) *types.Transaction {
-	t.Helper()
-
-	var (
-		key, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
-		testAddr = common.HexToAddress("0x7217d81b76bdd8707601e959454e3d776aee5f43")
-	)
-
-	tx, _ := types.SignTx(types.NewTx(&types.LegacyTx{
-		Nonce:    nonce,
-		To:       &testAddr,
-		Value:    value,
-		Gas:      gasLimit,
-		GasPrice: big.NewInt(1000000000),
-		Data:     data,
-	}), types.HomesteadSigner{}, key)
-
-	return tx
-}
-
 // setupBadBlock creates a bad block and stores it in the database for testing
 func setupBadBlock(t *testing.T, backend *testBackend, transactions []*types.Transaction) (*types.Block, []common.Hash) {
 	t.Helper()
@@ -1392,23 +1371,23 @@ func setupBadBlock(t *testing.T, backend *testBackend, transactions []*types.Tra
 	}
 
 	// Get the latest block from the test chain as the parent
-	latestBlock := backend.chain.CurrentBlock()
-	parentHash := latestBlock.Hash()
-	parentNumber := latestBlock.Number.Uint64()
+	parentBlock := backend.chain.CurrentBlock()
+	parentHash := parentBlock.Hash()
+	parentNumber := parentBlock.Number.Uint64()
 
 	// Create a bad block header that references the existing parent
 	badHeader := &types.Header{
 		Number:      big.NewInt(int64(parentNumber + 1)),
-		Time:        latestBlock.Time + 1,
+		Time:        parentBlock.Time + 1,
 		Extra:       []byte("bad block for testing"),
-		GasLimit:    latestBlock.GasLimit,
+		GasLimit:    parentBlock.GasLimit,
 		GasUsed:     uint64(len(transactions) * 21000),
 		Difficulty:  big.NewInt(1000),
 		UncleHash:   types.EmptyUncleHash,
 		TxHash:      types.DeriveSha(types.Transactions(transactions), trie.NewStackTrie(nil)),
 		ReceiptHash: types.EmptyReceiptsHash,
 		ParentHash:  parentHash,
-		BaseFee:     latestBlock.BaseFee, // Copy base fee to avoid nil pointer
+		BaseFee:     parentBlock.BaseFee, // Copy base fee to avoid nil pointer
 	}
 
 	// Create the bad block
@@ -1438,7 +1417,6 @@ func TestStandardTraceBadBlockToFile(t *testing.T) {
 	testAddr := common.HexToAddress("0x7217d81b76bdd8707601e959454e3d776aee5f43")
 	testCode := []byte{byte(vm.PUSH1), 0x42, byte(vm.POP), byte(vm.STOP)}
 
-	// Create test backend with proper accounts
 	genesis := &core.Genesis{
 		Config: params.TestChainConfig,
 		Alloc: types.GenesisAlloc{
@@ -1562,7 +1540,6 @@ func TestStandardTraceBadBlockToFile(t *testing.T) {
 				t.Fatalf("Expected %d trace files, got %d", len(tc.expectedTraces), len(files))
 			}
 
-			// Verify trace content if files are expected
 			for i, fileName := range files {
 				data, err := os.ReadFile(fileName)
 				if err != nil {