fix flaky test TestAllowedTxSize

core/txpool/legacypool/legacypool_test.go

@@ -116,6 +116,35 @@ func pricedDataTransaction(nonce uint64, gaslimit uint64, gasprice *big.Int, key
 	return tx
 }
 
+// pricedDataTransactionWithFixedSignature generates a signed transaction with fixed-size data,
+// and ensures that the resulting signature components (r and s) are exactly 32 bytes each.
+//
+// This avoids variability in transaction size caused by leading zeros being omitted in
+// RLP encoding of r/s. Since r and s are derived from ECDSA, they occasionally have leading
+// zeros and thus can be shorter than 32 bytes.
+//
+// For example:
+//
+//	r: 0 leading zeros, bytesSize: 32, bytes: [221 ... 101]
+//	s: 1 leading zeros, bytesSize: 31, bytes: [0 75 ... 47]
+//
+// This function retries signing up to 10 times to find a signature where both r and s are
+// exactly 32 bytes long.
+// 10 attempts is statistically sufficient since leading zeros in ECDSA signatures are rare and randomly distributed.
+//
+//	This ensures consistent transaction size (especially important when testing tx size limits).
+func pricedDataTransactionWithFixedSignature(nonce uint64, gaslimit uint64, gasprice *big.Int, key *ecdsa.PrivateKey, bytes uint64) *types.Transaction {
+	var tx *types.Transaction
+	for i := 0; i < 10; i++ {
+		tx = pricedDataTransaction(nonce, gaslimit, gasprice, key, bytes)
+		_, r, s := tx.RawSignatureValues()
+		if len(r.Bytes()) == 32 && len(s.Bytes()) == 32 {
+			break
+		}
+	}
+	return tx
+}
+
 func dynamicFeeTx(nonce uint64, gaslimit uint64, gasFee *big.Int, tip *big.Int, key *ecdsa.PrivateKey) *types.Transaction {
 	tx, _ := types.SignNewTx(key, types.LatestSignerForChainID(params.TestChainConfig.ChainID), &types.DynamicFeeTx{
 		ChainID:    params.TestChainConfig.ChainID,
@@ -1237,12 +1266,12 @@ func TestAllowedTxSize(t *testing.T) {
 	// Find the maximum data length for the kind of transaction which will
 	// be generated in the pool.addRemoteSync calls below.
 	const largeDataLength = txMaxSize - 200 // enough to have a 5 bytes RLP encoding of the data length number
-	txWithLargeData := pricedDataTransaction(0, pool.currentHead.Load().GasLimit, big.NewInt(1), key, largeDataLength)
+	txWithLargeData := pricedDataTransactionWithFixedSignature(0, pool.currentHead.Load().GasLimit, big.NewInt(1), key, largeDataLength)
 	maxTxLengthWithoutData := txWithLargeData.Size() - largeDataLength // 103 bytes
-	maxTxDataLength := txMaxSize - maxTxLengthWithoutData              // 131072 - 103 = 130953 bytes
+	maxTxDataLength := txMaxSize - maxTxLengthWithoutData              // 131072 - 103 = 130969 bytes
 
 	// Try adding a transaction with maximal allowed size
-	tx := pricedDataTransaction(0, pool.currentHead.Load().GasLimit, big.NewInt(1), key, maxTxDataLength)
+	tx := pricedDataTransactionWithFixedSignature(0, pool.currentHead.Load().GasLimit, big.NewInt(1), key, maxTxDataLength)
 	if err := pool.addRemoteSync(tx); err != nil {
 		t.Fatalf("failed to add transaction of size %d, close to maximal: %v", int(tx.Size()), err)
 	}
@@ -1251,7 +1280,7 @@ func TestAllowedTxSize(t *testing.T) {
 		t.Fatalf("failed to add transaction of random allowed size: %v", err)
 	}
 	// Try adding a transaction above maximum size by one
-	if err := pool.addRemoteSync(pricedDataTransaction(2, pool.currentHead.Load().GasLimit, big.NewInt(1), key, maxTxDataLength+1)); err == nil {
+	if err := pool.addRemoteSync(pricedDataTransactionWithFixedSignature(2, pool.currentHead.Load().GasLimit, big.NewInt(1), key, maxTxDataLength+1)); err == nil {
 		t.Fatalf("expected rejection on slightly oversize transaction")
 	}
 	// Try adding a transaction above maximum size by more than one