diff --git a/evm/pending_state/pending_ctx.go b/evm/pending_state/pending_ctx.go
index 09580cb..f0f5b74 100644
--- a/evm/pending_state/pending_ctx.go
+++ b/evm/pending_state/pending_ctx.go
@@ -2,7 +2,6 @@ package pending_state
 
 import (
 	"errors"
-	"fmt"
 	"sync"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -144,7 +143,7 @@ func (sctx *StateContext) SelfDestruct(addr common.Address, txnID int64) error {
 	}
 	if sctx.needCheck && sctx.WriteConflict(addr, txnID) {
 		sctx.meetConflict = true
-		return fmt.Errorf("conflict")
+		return errors.New("conflict")
 	}
 	sctx.Write.VisitDestruct(addr, txnID)
 	return nil
@@ -158,7 +157,7 @@ func (sctx *StateContext) WriteAccount(addr common.Address, txnID int64) error {
 	}
 	if sctx.needCheck && sctx.WriteConflict(addr, txnID) {
 		sctx.meetConflict = true
-		return fmt.Errorf("conflict")
+		return errors.New("conflict")
 	}
 	sctx.Write.VisitAccount(addr, txnID)
 	return nil
@@ -172,7 +171,7 @@ func (sctx *StateContext) WriteBalance(addr common.Address, txnID int64) error {
 	}
 	if sctx.needCheck && sctx.WriteConflict(addr, txnID) {
 		sctx.meetConflict = true
-		return fmt.Errorf("conflict")
+		return errors.New("conflict")
 	}
 	sctx.Write.VisitBalance(addr, txnID)
 	return nil
@@ -186,7 +185,7 @@ func (sctx *StateContext) ReadBalance(addr common.Address, txnID int64) error {
 	}
 	if sctx.needCheck && sctx.ReadConflict(addr, txnID) {
 		sctx.meetConflict = true
-		return fmt.Errorf("conflict")
+		return errors.New("conflict")
 	}
 	sctx.Read.VisitBalance(addr, txnID)
 	return nil
@@ -200,7 +199,7 @@ func (sctx *StateContext) WriteCode(addr common.Address, txnID int64) error {
 	}
 	if sctx.needCheck && sctx.WriteConflict(addr, txnID) {
 		sctx.meetConflict = true
-		return fmt.Errorf("conflict")
+		return errors.New("conflict")
 	}
 	sctx.Write.VisitCode(addr, txnID)
 	return nil
@@ -214,7 +213,7 @@ func (sctx *StateContext) ReadCode(addr common.Address, txnID int64) error {
 	}
 	if sctx.needCheck && sctx.ReadConflict(addr, txnID) {
 		sctx.meetConflict = true
-		return fmt.Errorf("conflict")
+		return errors.New("conflict")
 	}
 	sctx.Read.VisitCode(addr, txnID)
 	return nil
@@ -228,7 +227,7 @@ func (sctx *StateContext) WriteState(addr common.Address, key common.Hash, txnID
 	}
 	if sctx.needCheck && sctx.WriteConflict(addr, txnID) {
 		sctx.meetConflict = true
-		return fmt.Errorf("conflict")
+		return errors.New("conflict")
 	}
 	sctx.Write.VisitState(addr, key, txnID)
 	return nil
@@ -242,7 +241,7 @@ func (sctx *StateContext) ReadState(addr common.Address, key common.Hash, txnID
 	}
 	if sctx.needCheck && sctx.ReadConflict(addr, txnID) {
 		sctx.meetConflict = true
-		return fmt.Errorf("conflict")
+		return errors.New("conflict")
 	}
 	sctx.Read.VisitState(addr, key, txnID)
 	return nil
diff --git a/test/uniswap/uniswapTPS_testcase.go b/test/uniswap/uniswapTPS_testcase.go
index ec3b2bb..fbe8bec 100644
--- a/test/uniswap/uniswapTPS_testcase.go
+++ b/test/uniswap/uniswapTPS_testcase.go
@@ -132,7 +132,7 @@ func (cd *UniswapV2TPSStatisticsTestCase) prepareDeployerContract(deployerUser *
 		return [20]byte{}, nil, fmt.Errorf("Failed to confirm approve transaction: %v", err)
 	}
 	if !isConfirmed {
-		return [20]byte{}, nil, fmt.Errorf("transaction was not confirmed")
+		return [20]byte{}, nil, errors.New("transaction was not confirmed")
 	}
 	logrus.Info("deploy contracts done")
 	err = dispatchTestToken(client, depolyerAuth, ERC20DeployedContracts, testUsers, big.NewInt(accountInitialERC20Token))
diff --git a/test/uniswap/uniswapV2Accuracy_testcase.go b/test/uniswap/uniswapV2Accuracy_testcase.go
index 444fdf9..93645fc 100644
--- a/test/uniswap/uniswapV2Accuracy_testcase.go
+++ b/test/uniswap/uniswapV2Accuracy_testcase.go
@@ -225,7 +225,7 @@ func (ca *UniswapV2AccuracyTestCase) prepareDeployerContract(deployerUser *pkg.E
 		return [20]byte{}, nil, fmt.Errorf("Failed to confirm approve transaction: %v", err)
 	}
 	if !isConfirmed {
-		return [20]byte{}, nil, fmt.Errorf("transaction was not confirmed")
+		return [20]byte{}, nil, errors.New("transaction was not confirmed")
 	}
 	err = dispatchTestToken(client, depolyerAuth, ERC20DeployedContracts, testUsers, big.NewInt(accountInitialERC20Token))
 	if err != nil {