min and max offer amount checks (#445)

Co-authored-by: noot <36753753+noot@users.noreply.github.com>

cmd/swapcli/suite_test.go

@@ -23,7 +23,7 @@ type swapCLITestSuite struct {
 	mockTokens map[string]ethcommon.Address
 }
 
-func TestRunIntegrationTests(t *testing.T) {
+func TestRunSwapcliWithDaemonTests(t *testing.T) {
 	s := new(swapCLITestSuite)
 
 	s.conf = daemon.CreateTestConf(t, tests.GetMakerTestKey(t))

cmd/swapd/main.go

@@ -18,12 +18,12 @@ import (
 	"github.com/urfave/cli/v2"
 
 	"github.com/athanorlabs/atomic-swap/cliutil"
+	"github.com/athanorlabs/atomic-swap/coins"
 	"github.com/athanorlabs/atomic-swap/common"
 	mcrypto "github.com/athanorlabs/atomic-swap/crypto/monero"
 	"github.com/athanorlabs/atomic-swap/daemon"
 	"github.com/athanorlabs/atomic-swap/ethereum/extethclient"
 	"github.com/athanorlabs/atomic-swap/monero"
-	"github.com/athanorlabs/atomic-swap/relayer"
 )
 
 const (
@@ -209,7 +209,7 @@ func cliApp() *cli.App {
 				Name: flagRelayer,
 				Usage: fmt.Sprintf(
 					"Relay claims for XMR makers and earn %s ETH (minus gas fees) per transaction",
-					relayer.FeeEth.Text('f'),
+					coins.RelayerFeeETH.Text('f'),
 				),
 				Value: false,
 			},

codecov.yml

@@ -15,7 +15,7 @@ coverage:
 ignore:
   - ethereum/swap_creator.go
   - ethereum/aggregator_v3_interface.go
-  - ethereum/erc20_mock.go
+  - ethereum/erc20_token.go
   - ethereum/ierc20.go
   - ethereum/block/ut_contract_test.go
   - cmd/swapd/profile.go

coins/common.go

@@ -4,6 +4,8 @@
 package coins
 
 import (
+	"math/big"
+
 	"github.com/cockroachdb/apd/v3"
 	logging "github.com/ipfs/go-log"
 )
@@ -20,6 +22,13 @@ const (
 	MaxCoinPrecision = 100
 )
 
+// RelayerFeeWei and RelayerFeeETH are the fixed 0.009 ETH fee for using a swap
+// relayer to claim.
+var (
+	RelayerFeeWei = big.NewInt(9e15)
+	RelayerFeeETH = NewWeiAmount(RelayerFeeWei).AsEther()
+)
+
 var (
 	// decimalCtx is the apd context used for math operations on our coins
 	decimalCtx = apd.BaseContext.WithPrecision(MaxCoinPrecision)

common/types/offer.go

@@ -22,6 +22,12 @@ var (
 	// CurOfferVersion is the latest supported version of a serialised Offer struct
 	CurOfferVersion, _ = semver.NewVersion("1.0.0")
 
+	// Don't allow offers over 1000 XMR. Mainly to prevent fat-finger errors, it
+	// could be raised if users need it.
+	maxOfferValue = apd.New(1, 3) // 1000 XMR
+)
+
+var (
 	errOfferVersionMissing = errors.New(`required "version" field missing in offer`)
 	errOfferIDNotSet       = errors.New(`"offerID" is not set`)
 	errExchangeRateNil     = errors.New(`"exchangeRate" is not set`)
@@ -131,6 +137,7 @@ func (o *Offer) validate() error {
 		return err
 	}
 
+	// It is an error if the min is greater than the max
 	if o.MinAmount.Cmp(o.MaxAmount) > 0 {
 		return errMinGreaterThanMax
 	}
@@ -141,6 +148,25 @@ func (o *Offer) validate() error {
 		return errExchangeRateNil
 	}
 
+	// We want to prevent offers whose claim value is so low that a relayer
+	// can't be used to complete the swap if the maker does not have sufficient
+	// ETH to make the claim themselves. While relayers are not used with ERC20
+	// swaps, we still want a minimum swap amount, so we use the same value.
+	relayerFeeAsXMR, err := o.ExchangeRate.ToXMR(coins.RelayerFeeETH)
+	if err != nil {
+		return err
+	}
+	if o.MinAmount.Cmp(relayerFeeAsXMR) <= 0 {
+		return fmt.Errorf(
+			"min amount must be greater than %s ETH when converted (%s XMR)",
+			coins.RelayerFeeETH.Text('f'), relayerFeeAsXMR.Text('f'))
+	}
+
+	if o.MaxAmount.Cmp(maxOfferValue) > 0 {
+		return fmt.Errorf("%s XMR exceeds max offer amount of %s XMR",
+			o.MaxAmount.Text('f'), maxOfferValue.Text('f'))
+	}
+
 	if o.ID != o.hash() {
 		return errors.New("hash of offer fields does not match offer ID")
 	}

common/types/offer_test.go

@@ -175,6 +175,11 @@ func TestOffer_UnmarshalJSON_BadAmountsOrRate(t *testing.T) {
 			jsonData:    fmt.Sprintf(offerJSON, `"-1"`, `"1"`, `"0.1"`),
 			errContains: `"minAmount" cannot be negative`,
 		},
+		{
+			// 0.009 relayer fee is 0.09 XMR with exchange rate of 0.1
+			jsonData:    fmt.Sprintf(offerJSON, `"0.09"`, `"10"`, `"0.1"`),
+			errContains: `min amount must be greater than 0.009 ETH when converted (0.09 XMR)`,
+		},
 		// Max Amount checks
 		{
 			jsonData:    fmt.Sprintf(offerJSON, `"1"`, `null`, `"0.1"`),
@@ -188,6 +193,10 @@ func TestOffer_UnmarshalJSON_BadAmountsOrRate(t *testing.T) {
 			jsonData:    fmt.Sprintf(offerJSON, `"1"`, `"-1E1"`, `"0.1"`),
 			errContains: `"maxAmount" cannot be negative`,
 		},
+		{
+			jsonData:    fmt.Sprintf(offerJSON, `"100"`, `"1000.1"`, `"0.1"`),
+			errContains: `1000.1 XMR exceeds max offer amount of 1000 XMR`,
+		},
 		// Combo min/max check
 		{
 			jsonData:    fmt.Sprintf(offerJSON, `"0.11"`, `"0.1"`, `"0.1"`),

daemon/swap_daemon_test.go

@@ -27,7 +27,6 @@ import (
 	"github.com/athanorlabs/atomic-swap/ethereum/extethclient"
 	"github.com/athanorlabs/atomic-swap/monero"
 	"github.com/athanorlabs/atomic-swap/net"
-	"github.com/athanorlabs/atomic-swap/relayer"
 	"github.com/athanorlabs/atomic-swap/rpcclient"
 	"github.com/athanorlabs/atomic-swap/rpcclient/wsclient"
 	"github.com/athanorlabs/atomic-swap/tests"
@@ -184,7 +183,7 @@ func TestRunSwapDaemon_SwapBobHasNoEth_AliceRelaysClaim(t *testing.T) {
 	// Bob's ending balance should be Alice's provided amount minus the relayer fee
 	//
 	expectedBal := new(apd.Decimal)
-	_, err = coins.DecimalCtx().Sub(expectedBal, providesAmt, relayer.FeeEth)
+	_, err = coins.DecimalCtx().Sub(expectedBal, providesAmt, coins.RelayerFeeETH)
 	require.NoError(t, err)
 
 	bobBalance, err := bobConf.EthereumClient.Balance(ctx)
@@ -362,7 +361,7 @@ func TestRunSwapDaemon_CharlieRelays(t *testing.T) {
 	// Bob's ending balance should be Alice's provided amount minus the relayer fee
 	//
 	bobExpectedBal := new(apd.Decimal)
-	_, err = coins.DecimalCtx().Sub(bobExpectedBal, providesAmt, relayer.FeeEth)
+	_, err = coins.DecimalCtx().Sub(bobExpectedBal, providesAmt, coins.RelayerFeeETH)
 	require.NoError(t, err)
 	bobBalance, err := bobConf.EthereumClient.Balance(ctx)
 	require.NoError(t, err)
@@ -467,7 +466,7 @@ func TestRunSwapDaemon_CharlieIsBroke_AliceRelays(t *testing.T) {
 	// Bob's ending balance should be Alice's provided amount minus the relayer fee
 	//
 	bobExpectedBal := new(apd.Decimal)
-	_, err = coins.DecimalCtx().Sub(bobExpectedBal, providesAmt, relayer.FeeEth)
+	_, err = coins.DecimalCtx().Sub(bobExpectedBal, providesAmt, coins.RelayerFeeETH)
 	require.NoError(t, err)
 	bobBalance, err := bobConf.EthereumClient.Balance(ctx)
 	require.NoError(t, err)

ethereum/check_swap_creator_contract_test.go

@@ -6,46 +6,24 @@ package contracts
 import (
 	"bytes"
 	"context"
-	"crypto/ecdsa"
 	"errors"
 	"testing"
 
 	"github.com/athanorlabs/go-relayer/impls/gsnforwarder"
 	ethcommon "github.com/ethereum/go-ethereum/common"
 	ethcrypto "github.com/ethereum/go-ethereum/crypto"
-	"github.com/ethereum/go-ethereum/ethclient"
 	"github.com/stretchr/testify/require"
 
 	"github.com/athanorlabs/atomic-swap/common"
 	"github.com/athanorlabs/atomic-swap/tests"
 )
 
-// deployContract is a test helper that deploys the SwapCreator contract and returns the
-// deployed address
-func deployContract(
-	t *testing.T,
-	ec *ethclient.Client,
-	pk *ecdsa.PrivateKey,
-	trustedForwarder ethcommon.Address,
-) ethcommon.Address {
-	ctx := context.Background()
-	contractAddr, _, err := DeploySwapCreatorWithKey(ctx, ec, pk, trustedForwarder)
-	require.NoError(t, err)
-	return contractAddr
-}
-
-func deployForwarder(t *testing.T, ec *ethclient.Client, pk *ecdsa.PrivateKey) ethcommon.Address {
-	addr, err := DeployGSNForwarderWithKey(context.Background(), ec, pk)
-	require.NoError(t, err)
-	return addr
-}
-
 // getContractCode is a test helper that deploys the swap creator contract to read back
 // and return the finalised byte code post deployment.
-func getContractCode(t *testing.T, trustedForwarder ethcommon.Address) []byte {
+func getContractCode(t *testing.T, forwarderAddr ethcommon.Address) []byte {
 	ec, _ := tests.NewEthClient(t)
 	pk := tests.GetMakerTestKey(t)
-	contractAddr := deployContract(t, ec, pk, trustedForwarder)
+	contractAddr, _ := deploySwapCreatorWithForwarder(t, ec, pk, forwarderAddr)
 	code, err := ec.CodeAt(context.Background(), contractAddr, nil)
 	require.NoError(t, err)
 	return code
@@ -54,8 +32,8 @@ func getContractCode(t *testing.T, trustedForwarder ethcommon.Address) []byte {
 func TestCheckForwarderContractCode(t *testing.T) {
 	ec, _ := tests.NewEthClient(t)
 	pk := tests.GetMakerTestKey(t)
-	trustedForwarder := deployForwarder(t, ec, pk)
+	forwarderAddr := deployForwarder(t, ec, pk)
-	err := CheckForwarderContractCode(context.Background(), ec, trustedForwarder)
+	err := CheckForwarderContractCode(context.Background(), ec, forwarderAddr)
 	require.NoError(t, err)
 }
 
@@ -66,7 +44,7 @@ func TestExpectedSwapCreatorBytecodeHex(t *testing.T) {
 	allZeroTrustedForwarder := ethcommon.Address{}
 	codeHex := ethcommon.Bytes2Hex(getContractCode(t, allZeroTrustedForwarder))
 	require.Equal(t, expectedSwapCreatorBytecodeHex, codeHex,
-		"update the expectedSwapCreatorBytecodeHex constant with the actual value tocat  fix this test")
+		"update the expectedSwapCreatorBytecodeHex constant with the actual value to fix this test")
 }
 
 // This test will fail if the compiled SwapCreator contract is updated, but the
@@ -75,12 +53,12 @@ func TestExpectedSwapCreatorBytecodeHex(t *testing.T) {
 func TestForwarderAddrIndexes(t *testing.T) {
 	ec, _ := tests.NewEthClient(t)
 	pk := tests.GetMakerTestKey(t)
-	trustedForwarder := deployForwarder(t, ec, pk)
+	forwarderAddr := deployForwarder(t, ec, pk)
-	contactBytes := getContractCode(t, trustedForwarder)
+	contactBytes := getContractCode(t, forwarderAddr)
 
 	addressLocations := make([]int, 0) // at the current time, there should always be 2
 	for i := 0; i < len(contactBytes)-ethAddrByteLen; i++ {
-		if bytes.Equal(contactBytes[i:i+ethAddrByteLen], trustedForwarder[:]) {
+		if bytes.Equal(contactBytes[i:i+ethAddrByteLen], forwarderAddr[:]) {
 			addressLocations = append(addressLocations, i)
 			i += ethAddrByteLen - 1 // -1 since the loop will increment by 1
 		}
@@ -96,15 +74,15 @@ func TestForwarderAddrIndexes(t *testing.T) {
 func TestCheckSwapCreatorContractCode(t *testing.T) {
 	ec, _ := tests.NewEthClient(t)
 	pk := tests.GetMakerTestKey(t)
-	trustedForwarderAddrs := []string{
+	forwarderAddrs := []string{
 		deployForwarder(t, ec, pk).Hex(),
 		deployForwarder(t, ec, pk).Hex(),
 		deployForwarder(t, ec, pk).Hex(),
 	}
 
-	for _, addrHex := range trustedForwarderAddrs {
+	for _, addrHex := range forwarderAddrs {
 		tfAddr := ethcommon.HexToAddress(addrHex)
-		contractAddr := deployContract(t, ec, pk, tfAddr)
+		contractAddr, _ := deploySwapCreatorWithForwarder(t, ec, pk, tfAddr)
 		parsedTFAddr, err := CheckSwapCreatorContractCode(context.Background(), ec, contractAddr)
 		require.NoError(t, err)
 		require.Equal(t, addrHex, parsedTFAddr.Hex())

ethereum/consts.go

@@ -0,0 +1,15 @@
+package contracts
+
+// Gas prices for our operations. Most of these are set by the highest value we
+// ever see in a test, so you would need to adjust upwards a little to use as a
+// gas limit. We use these values to estimate minimum required balances.
+const (
+	MaxNewSwapETHGas   = 50589
+	MaxNewSwapTokenGas = 86218
+	MaxSetReadyGas     = 31872
+	MaxClaimETHGas     = 43349
+	MaxClaimTokenGas   = 47522
+	MaxRefundETHGas    = 43120
+	MaxRefundTokenGas  = 47282
+	MaxTokenApproveGas = 47000 // 46223 with our contract
+)

ethereum/consts_test.go

@@ -0,0 +1,8 @@
+package contracts
+
+// We don't deploy SwapCreator contracts or ERC20 token contracts in swaps, so
+// these constants are only compiled in for test files.
+const (
+	maxSwapCreatorDeployGas = 1005177
+	maxTestERC20DeployGas   = 798226 // using long token names or symbols will increase this
+)

ethereum/erc20_mock_test.go

@@ -1,80 +0,0 @@
-// Copyright 2023 The AthanorLabs/atomic-swap Authors
-// SPDX-License-Identifier: LGPL-3.0-only
-
-package contracts
-
-import (
-	"context"
-	"crypto/ecdsa"
-	"math/big"
-	"testing"
-
-	"github.com/ethereum/go-ethereum/crypto"
-	"github.com/stretchr/testify/require"
-
-	"github.com/athanorlabs/atomic-swap/ethereum/block"
-)
-
-func TestSwapCreator_NewSwap_ERC20(t *testing.T) {
-	auth, conn, pkA := setupXMRTakerAuth(t)
-	pub := pkA.Public().(*ecdsa.PublicKey)
-	addr := crypto.PubkeyToAddress(*pub)
-
-	// deploy TestERC20
-	erc20Addr, erc20Tx, erc20Contract, err :=
-		DeployTestERC20(auth, conn, "TestERC20", "MOCK", 18, addr, big.NewInt(9999))
-	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, erc20Tx.Hash())
-	require.NoError(t, err)
-	t.Logf("gas cost to deploy TestERC20.sol: %d", receipt.GasUsed)
-
-	testNewSwap(t, erc20Addr, erc20Contract)
-}
-
-func TestSwapCreator_Claim_ERC20(t *testing.T) {
-	auth, conn, pkA := setupXMRTakerAuth(t)
-	pub := pkA.Public().(*ecdsa.PublicKey)
-	addr := crypto.PubkeyToAddress(*pub)
-
-	erc20Addr, erc20Tx, erc20Contract, err := DeployTestERC20(auth, conn, "TestERC20", "TEST", 18, addr, big.NewInt(9999))
-	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, erc20Tx.Hash())
-	require.NoError(t, err)
-	t.Logf("gas cost to deploy TestERC20.sol: %d", receipt.GasUsed)
-
-	// 3 logs:
-	// Approval
-	// Transfer
-	// New
-	testClaim(t, erc20Addr, 2, big.NewInt(99), erc20Contract)
-}
-
-func TestSwapCreator_RefundBeforeT0_ERC20(t *testing.T) {
-	auth, conn, pkA := setupXMRTakerAuth(t)
-	pub := pkA.Public().(*ecdsa.PublicKey)
-	addr := crypto.PubkeyToAddress(*pub)
-
-	erc20Addr, erc20Tx, erc20Contract, err :=
-		DeployTestERC20(auth, conn, "TestERC20", "TEST", 18, addr, big.NewInt(9999))
-	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, erc20Tx.Hash())
-	require.NoError(t, err)
-	t.Logf("gas cost to deploy TestERC20.sol: %d", receipt.GasUsed)
-
-	testRefundBeforeT0(t, erc20Addr, erc20Contract, 2)
-}
-
-func TestSwapCreator_RefundAfterT1_ERC20(t *testing.T) {
-	auth, conn, pkA := setupXMRTakerAuth(t)
-	pub := pkA.Public().(*ecdsa.PublicKey)
-	addr := crypto.PubkeyToAddress(*pub)
-
-	erc20Addr, erc20Tx, erc20Contract, err :=
-		DeployTestERC20(auth, conn, "TestERC20", "TestERC20", 18, addr, big.NewInt(9999))
-	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, erc20Tx.Hash())
-	require.NoError(t, err)
-	t.Logf("gas cost to deploy TestERC20.sol: %d", receipt.GasUsed)
-
-	testRefundAfterT1(t, erc20Addr, erc20Contract, 2)
-}

ethereum/erc20_token_test.go

@@ -0,0 +1,84 @@
+// Copyright 2023 The AthanorLabs/atomic-swap Authors
+// SPDX-License-Identifier: LGPL-3.0-only
+
+package contracts
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/stretchr/testify/require"
+
+	"github.com/athanorlabs/atomic-swap/common/types"
+	"github.com/athanorlabs/atomic-swap/tests"
+)
+
+func TestSwapCreator_NewSwap_ERC20(t *testing.T) {
+	pkA := tests.GetTakerTestKey(t)
+	ec, _ := tests.NewEthClient(t)
+	addr := crypto.PubkeyToAddress(pkA.PublicKey)
+
+	// deploy TestERC20
+	erc20Addr, tx, erc20Contract, err :=
+		DeployTestERC20(getAuth(t, pkA), ec, "Test of the ERC20 Token", "ERC20Token", 18, addr, big.NewInt(9999))
+	require.NoError(t, err)
+	receipt := getReceipt(t, ec, tx)
+	t.Logf("gas cost to deploy TestERC20.sol: %d (delta %d)",
+		receipt.GasUsed, maxTestERC20DeployGas-int(receipt.GasUsed))
+	require.GreaterOrEqual(t, maxTestERC20DeployGas, int(receipt.GasUsed))
+
+	testNewSwap(t, types.EthAsset(erc20Addr), erc20Contract)
+}
+
+func TestSwapCreator_Claim_ERC20(t *testing.T) {
+	pkA := tests.GetTakerTestKey(t)
+	ec, _ := tests.NewEthClient(t)
+	addr := crypto.PubkeyToAddress(pkA.PublicKey)
+
+	erc20Addr, tx, erc20Contract, err :=
+		DeployTestERC20(getAuth(t, pkA), ec, "TestERC20", "TEST", 18, addr, big.NewInt(9999))
+	require.NoError(t, err)
+	receipt := getReceipt(t, ec, tx)
+	t.Logf("gas cost to deploy TestERC20.sol: %d (delta %d)",
+		receipt.GasUsed, maxTestERC20DeployGas-int(receipt.GasUsed))
+	require.GreaterOrEqual(t, maxTestERC20DeployGas, int(receipt.GasUsed))
+
+	// 3 logs:
+	// Approval
+	// Transfer
+	// New
+	testClaim(t, types.EthAsset(erc20Addr), 2, big.NewInt(99), erc20Contract)
+}
+
+func TestSwapCreator_RefundBeforeT0_ERC20(t *testing.T) {
+	pkA := tests.GetTakerTestKey(t)
+	ec, _ := tests.NewEthClient(t)
+	addr := crypto.PubkeyToAddress(pkA.PublicKey)
+
+	erc20Addr, tx, erc20Contract, err :=
+		DeployTestERC20(getAuth(t, pkA), ec, "TestERC20", "TEST", 18, addr, big.NewInt(9999))
+	require.NoError(t, err)
+	receipt := getReceipt(t, ec, tx)
+	t.Logf("gas cost to deploy TestERC20.sol: %d (delta %d)",
+		receipt.GasUsed, maxTestERC20DeployGas-int(receipt.GasUsed))
+	require.GreaterOrEqual(t, maxTestERC20DeployGas, int(receipt.GasUsed))
+
+	testRefundBeforeT0(t, types.EthAsset(erc20Addr), erc20Contract, 2)
+}
+
+func TestSwapCreator_RefundAfterT1_ERC20(t *testing.T) {
+	pkA := tests.GetTakerTestKey(t)
+	ec, _ := tests.NewEthClient(t)
+	addr := crypto.PubkeyToAddress(pkA.PublicKey)
+
+	erc20Addr, tx, erc20Contract, err :=
+		DeployTestERC20(getAuth(t, pkA), ec, "TestERC20", "TestERC20", 18, addr, big.NewInt(9999))
+	require.NoError(t, err)
+	receipt := getReceipt(t, ec, tx)
+	t.Logf("gas cost to deploy TestERC20.sol: %d (delta %d)",
+		receipt.GasUsed, maxTestERC20DeployGas-int(receipt.GasUsed))
+	require.GreaterOrEqual(t, maxTestERC20DeployGas, int(receipt.GasUsed))
+
+	testRefundAfterT1(t, types.EthAsset(erc20Addr), erc20Contract, 2)
+}

ethereum/swap_creator_test.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	ethcommon "github.com/ethereum/go-ethereum/common"
+	ethtypes "github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethclient"
 	"github.com/stretchr/testify/require"
@@ -29,53 +30,78 @@ import (
 
 var (
 	defaultTimeoutDuration = big.NewInt(60) // 60 seconds
-	ethAssetAddress        = ethcommon.Address(types.EthAssetETH)
 	defaultSwapValue       = big.NewInt(100)
 	dummySwapKey           = [32]byte{1} // dummy non-zero value for claim/refund key
 )
 
-func setupXMRTakerAuth(t *testing.T) (*bind.TransactOpts, *ethclient.Client, *ecdsa.PrivateKey) {
+func getAuth(t *testing.T, pk *ecdsa.PrivateKey) *bind.TransactOpts {
-	conn, _ := tests.NewEthClient(t)
+	txOpts, err := bind.NewKeyedTransactorWithChainID(pk, big.NewInt(common.GanacheChainID))
-	pkA := tests.GetTakerTestKey(t)
-	chainID, err := conn.ChainID(context.Background())
 	require.NoError(t, err)
-	auth, err := bind.NewKeyedTransactorWithChainID(pkA, chainID)
+	return txOpts
+}
+
+func getReceipt(t *testing.T, ec *ethclient.Client, tx *ethtypes.Transaction) *ethtypes.Receipt {
+	receipt, err := block.WaitForReceipt(context.Background(), ec, tx.Hash())
 	require.NoError(t, err)
-	return auth, conn, pkA
+	return receipt
 }
 
 func approveERC20(t *testing.T,
-	auth *bind.TransactOpts,
+	ec *ethclient.Client,
-	conn *ethclient.Client,
+	pk *ecdsa.PrivateKey,
 	erc20Contract *TestERC20,
 	swapCreatorAddress ethcommon.Address,
 	value *big.Int,
 ) {
 	require.NotNil(t, erc20Contract)
-	tx, err := erc20Contract.Approve(auth, swapCreatorAddress, value)
+
+	tx, err := erc20Contract.Approve(getAuth(t, pk), swapCreatorAddress, value)
 	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	receipt := getReceipt(t, ec, tx)
-	require.NoError(t, err)
+
-	t.Logf("gas cost to call Approve: %d", receipt.GasUsed)
+	t.Logf("gas cost to call Approve %d (delta %d)", receipt.GasUsed, MaxTokenApproveGas-int(receipt.GasUsed))
+	require.GreaterOrEqual(t, MaxTokenApproveGas, int(receipt.GasUsed), "Token Approve")
 }
 
-func testNewSwap(t *testing.T, asset ethcommon.Address, erc20Contract *TestERC20) {
+func deployForwarder(t *testing.T, ec *ethclient.Client, pk *ecdsa.PrivateKey) ethcommon.Address {
-	auth, conn, _ := setupXMRTakerAuth(t)
+	forwarderAddr, err := DeployGSNForwarderWithKey(context.Background(), ec, pk)
-	address, tx, contract, err := DeploySwapCreator(auth, conn, ethcommon.Address{})
 	require.NoError(t, err)
-	require.NotEqual(t, ethcommon.Address{}, address)
+	return forwarderAddr
-	require.NotNil(t, tx)
+}
-	require.NotNil(t, contract)
 
-	receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
+func deploySwapCreatorWithForwarder(
+	t *testing.T,
+	ec *ethclient.Client,
+	pk *ecdsa.PrivateKey,
+	forwarderAddr ethcommon.Address,
+) (ethcommon.Address, *SwapCreator) {
+	swapCreatorAddr, tx, swapCreator, err := DeploySwapCreator(getAuth(t, pk), ec, forwarderAddr)
 	require.NoError(t, err)
-	t.Logf("gas cost to deploy SwapCreator.sol: %d", receipt.GasUsed)
+	receipt := getReceipt(t, ec, tx)
 
-	owner := auth.From
+	t.Logf("gas cost to deploy SwapCreator.sol: %d (delta %d)",
+		receipt.GasUsed, maxSwapCreatorDeployGas-int(receipt.GasUsed))
+	require.GreaterOrEqual(t, maxSwapCreatorDeployGas, int(receipt.GasUsed), "deploy SwapCreator")
+
+	return swapCreatorAddr, swapCreator
+}
+
+func deploySwapCreator(t *testing.T, ec *ethclient.Client, pk *ecdsa.PrivateKey) (ethcommon.Address, *SwapCreator) {
+	forwarderAddr := deployForwarder(t, ec, pk)
+	return deploySwapCreatorWithForwarder(t, ec, pk, forwarderAddr)
+}
+
+func testNewSwap(t *testing.T, asset types.EthAsset, erc20Contract *TestERC20) {
+	pk := tests.GetTakerTestKey(t)
+	ec, _ := tests.NewEthClient(t)
+
+	swapCreatorAddr, swapCreator := deploySwapCreator(t, ec, pk)
+
+	owner := crypto.PubkeyToAddress(pk.PublicKey)
 	claimer := common.EthereumPrivateKeyToAddress(tests.GetMakerTestKey(t))
 
 	var pubKeyClaim, pubKeyRefund [32]byte
-	_, err = rand.Read(pubKeyClaim[:])
+	_, err := rand.Read(pubKeyClaim[:])
 	require.NoError(t, err)
 	_, err = rand.Read(pubKeyRefund[:])
 	require.NoError(t, err)
@@ -83,34 +109,40 @@ func testNewSwap(t *testing.T, asset ethcommon.Address, erc20Contract *TestERC20
 	nonce, err := rand.Prime(rand.Reader, 256)
 	require.NoError(t, err)
 
+	txOpts := getAuth(t, pk)
 	value := defaultSwapValue
-	isEthAsset := asset == ethAssetAddress
+	if asset.IsETH() {
-
+		txOpts.Value = value
-	if isEthAsset {
-		auth.Value = value
 	} else {
-		approveERC20(t, auth, conn, erc20Contract, address, value)
+		approveERC20(t, ec, pk, erc20Contract, swapCreatorAddr, value)
 	}
 
-	tx, err = contract.NewSwap(
+	tx, err := swapCreator.NewSwap(
-		auth,
+		txOpts,
 		pubKeyClaim,
 		pubKeyRefund,
 		claimer,
 		defaultTimeoutDuration,
 		defaultTimeoutDuration,
-		asset,
+		asset.Address(),
 		value,
 		nonce,
 	)
 	require.NoError(t, err)
 
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	receipt := getReceipt(t, ec, tx)
-	require.NoError(t, err)
+	if asset.IsETH() {
-	t.Logf("gas cost to call new_swap: %d", receipt.GasUsed)
+		t.Logf("gas cost to call ETH NewSwap: %d (delta %d)",
+			receipt.GasUsed, MaxNewSwapETHGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxNewSwapETHGas, int(receipt.GasUsed), "ETH NewSwap")
+	} else {
+		t.Logf("gas cost to call token NewSwap: %d (delta %d)",
+			receipt.GasUsed, MaxNewSwapTokenGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxNewSwapTokenGas, int(receipt.GasUsed), "Token NewSwap")
+	}
 
 	newSwapLogIndex := 0
-	if !isEthAsset {
+	if asset.IsToken() {
 		newSwapLogIndex = 2
 	}
 	require.Equal(t, newSwapLogIndex+1, len(receipt.Logs))
@@ -129,7 +161,7 @@ func testNewSwap(t *testing.T, asset ethcommon.Address, erc20Contract *TestERC20
 		PubKeyRefund: pubKeyRefund,
 		Timeout0:     t0,
 		Timeout1:     t1,
-		Asset:        asset,
+		Asset:        asset.Address(),
 		Value:        value,
 		Nonce:        nonce,
 	}
@@ -139,7 +171,7 @@ func testNewSwap(t *testing.T, asset ethcommon.Address, erc20Contract *TestERC20
 }
 
 func TestSwapCreator_NewSwap(t *testing.T) {
-	testNewSwap(t, ethAssetAddress, nil)
+	testNewSwap(t, types.EthAssetETH, nil)
 }
 
 func TestSwapCreator_Claim_vec(t *testing.T) {
@@ -159,26 +191,23 @@ func TestSwapCreator_Claim_vec(t *testing.T) {
 	cmt := pk.Keccak256()
 
 	// deploy swap contract with claim key hash
-	auth, conn, pkA := setupXMRTakerAuth(t)
+	pkA := tests.GetTakerTestKey(t)
-	pub := pkA.Public().(*ecdsa.PublicKey)
+	ec, _ := tests.NewEthClient(t)
-	addr := crypto.PubkeyToAddress(*pub)
+	addr := crypto.PubkeyToAddress(pkA.PublicKey)
 
-	_, tx, contract, err := DeploySwapCreator(auth, conn, ethcommon.Address{})
+	_, swapCreator := deploySwapCreator(t, ec, pkA)
-	require.NoError(t, err)
+
-	receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	txOpts := getAuth(t, pkA)
-	require.NoError(t, err)
+	txOpts.Value = defaultSwapValue
-	t.Logf("gas cost to deploy SwapCreator.sol: %d", receipt.GasUsed)
 
 	nonce := big.NewInt(0)
-	auth.Value = defaultSwapValue
+	tx, err := swapCreator.NewSwap(txOpts, cmt, dummySwapKey, addr, defaultTimeoutDuration,
-	tx, err = contract.NewSwap(auth, cmt, dummySwapKey, addr, defaultTimeoutDuration,
 		defaultTimeoutDuration, ethcommon.Address(types.EthAssetETH), defaultSwapValue, nonce)
 	require.NoError(t, err)
-	auth.Value = nil
 
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	receipt := getReceipt(t, ec, tx)
-	require.NoError(t, err)
+	t.Logf("gas cost to call ETH NewSwap: %d (delta %d)", receipt.GasUsed, MaxNewSwapETHGas-int(receipt.GasUsed))
-	t.Logf("gas cost to call new_swap: %d", receipt.GasUsed)
+	require.GreaterOrEqual(t, MaxNewSwapETHGas, int(receipt.GasUsed), "ETH NewSwap")
 
 	require.Equal(t, 1, len(receipt.Logs))
 	id, err := GetIDFromLog(receipt.Logs[0])
@@ -200,25 +229,26 @@ func TestSwapCreator_Claim_vec(t *testing.T) {
 	}
 
 	// set contract to Ready
-	tx, err = contract.SetReady(auth, swap)
+	tx, err = swapCreator.SetReady(getAuth(t, pkA), swap)
 	require.NoError(t, err)
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	receipt = getReceipt(t, ec, tx)
-	require.NoError(t, err)
+
-	t.Logf("gas cost to call set_ready: %d", receipt.GasUsed)
+	t.Logf("gas cost to call SetReady: %d (delta %d)", receipt.GasUsed, MaxSetReadyGas-int(receipt.GasUsed))
+	require.GreaterOrEqual(t, MaxSetReadyGas, int(receipt.GasUsed), "SetReady")
 
 	// now let's try to claim
-	tx, err = contract.Claim(auth, swap, s)
+	tx, err = swapCreator.Claim(getAuth(t, pkA), swap, s)
 	require.NoError(t, err)
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	receipt = getReceipt(t, ec, tx)
-	require.NoError(t, err)
+	t.Logf("gas cost to call ETH Claim: %d (delta %d)", receipt.GasUsed, MaxClaimETHGas-int(receipt.GasUsed))
-	t.Logf("gas cost to call claim: %d", receipt.GasUsed)
+	require.GreaterOrEqual(t, MaxClaimETHGas, int(receipt.GasUsed), "ETH Claim")
 
-	stage, err := contract.Swaps(nil, id)
+	stage, err := swapCreator.Swaps(nil, id)
 	require.NoError(t, err)
 	require.Equal(t, StageCompleted, stage)
 }
 
-func testClaim(t *testing.T, asset ethcommon.Address, newLogIndex int, value *big.Int, erc20Contract *TestERC20) {
+func testClaim(t *testing.T, asset types.EthAsset, newLogIndex int, value *big.Int, erc20Contract *TestERC20) {
 	// generate claim secret and public key
 	dleq := &dleq.DefaultDLEq{}
 	proof, err := dleq.Prove()
@@ -230,36 +260,37 @@ func testClaim(t *testing.T, asset ethcommon.Address, newLogIndex int, value *bi
 	cmt := res.Secp256k1PublicKey().Keccak256()
 
 	// deploy swap contract with claim key hash
-	authOrig, conn, pkA := setupXMRTakerAuth(t)
+	pkA := tests.GetTakerTestKey(t)
-	pub := pkA.Public().(*ecdsa.PublicKey)
+	ec, _ := tests.NewEthClient(t)
-	addr := crypto.PubkeyToAddress(*pub)
+	addr := crypto.PubkeyToAddress(pkA.PublicKey)
 
-	// TODO: Rewrite this code to avoid the awkward use of txOpts. Code was using
+	swapCreatorAddr, swapCreator := deploySwapCreator(t, ec, pkA)
-	//       same TxOpts for multiple transactions and we needed a quick fix to get
-	//       CI working.
-	txOpts := *authOrig
-	swapCreatorAddr, tx, contract, err := DeploySwapCreator(&txOpts, conn, ethcommon.Address{})
-	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
-	require.NoError(t, err)
-	t.Logf("gas cost to deploy SwapCreator.sol: %d", receipt.GasUsed)
 
-	if asset != ethAssetAddress {
+	if asset.IsToken() {
-		approveERC20(t, authOrig, conn, erc20Contract, swapCreatorAddr, value)
+		approveERC20(t, ec, pkA, erc20Contract, swapCreatorAddr, value)
 	}
 
-	nonce := big.NewInt(0)
+	txOpts := getAuth(t, pkA)
-	txOpts = *authOrig
+	require.NoError(t, err)
-	if asset == ethAssetAddress {
+	if asset.IsETH() {
 		txOpts.Value = value
 	}
 
-	tx, err = contract.NewSwap(&txOpts, cmt, dummySwapKey, addr,
+	nonce := GenerateNewSwapNonce()
-		defaultTimeoutDuration, defaultTimeoutDuration, asset, value, nonce)
+	tx, err := swapCreator.NewSwap(txOpts, cmt, dummySwapKey, addr,
+		defaultTimeoutDuration, defaultTimeoutDuration, asset.Address(), value, nonce)
 	require.NoError(t, err)
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+
-	require.NoError(t, err)
+	receipt := getReceipt(t, ec, tx)
-	t.Logf("gas cost to call new_swap: %d", receipt.GasUsed)
+	if asset.IsETH() {
+		t.Logf("gas cost to call ETH NewSwap: %d (delta %d)",
+			receipt.GasUsed, MaxNewSwapETHGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxNewSwapETHGas, int(receipt.GasUsed), "ETH NewSwap")
+	} else {
+		t.Logf("gas cost to call token NewSwap: %d (delta %d)",
+			receipt.GasUsed, MaxNewSwapTokenGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxNewSwapTokenGas, int(receipt.GasUsed), "Token NewSwap")
+	}
 
 	require.Equal(t, newLogIndex+1, len(receipt.Logs))
 	id, err := GetIDFromLog(receipt.Logs[newLogIndex])
@@ -275,42 +306,45 @@ func testClaim(t *testing.T, asset ethcommon.Address, newLogIndex int, value *bi
 		PubKeyRefund: dummySwapKey,
 		Timeout0:     t0,
 		Timeout1:     t1,
-		Asset:        asset,
+		Asset:        asset.Address(),
 		Value:        value,
 		Nonce:        nonce,
 	}
 
 	// ensure we can't claim before setting contract to Ready
-	txOpts = *authOrig
+	_, err = swapCreator.Claim(getAuth(t, pkA), swap, proof.Secret())
-	_, err = contract.Claim(&txOpts, swap, proof.Secret())
 	require.ErrorContains(t, err, "VM Exception while processing transaction: revert")
 
 	// set contract to Ready
-	txOpts = *authOrig
+	tx, err = swapCreator.SetReady(getAuth(t, pkA), swap)
-	tx, err = contract.SetReady(&txOpts, swap)
-	require.NoError(t, err)
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
-	t.Logf("gas cost to call SetReady: %d", receipt.GasUsed)
 	require.NoError(t, err)
+	receipt = getReceipt(t, ec, tx)
+	t.Logf("gas cost to call SetReady: %d (delta %d)", receipt.GasUsed, MaxSetReadyGas-int(receipt.GasUsed))
+	require.GreaterOrEqual(t, MaxSetReadyGas, int(receipt.GasUsed), "SetReady")
 
 	// now let's try to claim
-	txOpts = *authOrig
+	tx, err = swapCreator.Claim(getAuth(t, pkA), swap, proof.Secret())
-	tx, err = contract.Claim(&txOpts, swap, proof.Secret())
 	require.NoError(t, err)
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	receipt = getReceipt(t, ec, tx)
-	require.NoError(t, err)
-	t.Logf("gas cost to call Claim: %d", receipt.GasUsed)
 
-	stage, err := contract.Swaps(nil, id)
+	if asset.IsETH() {
+		t.Logf("gas cost to call ETH Claim: %d (delta %d)", receipt.GasUsed, MaxClaimETHGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxClaimETHGas, int(receipt.GasUsed), "ETH Claim")
+	} else {
+		t.Logf("gas cost to call token Claim: %d (delta %d)", receipt.GasUsed, MaxClaimTokenGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxClaimTokenGas, int(receipt.GasUsed), "Token Claim")
+	}
+
+	stage, err := swapCreator.Swaps(nil, id)
 	require.NoError(t, err)
 	require.Equal(t, StageCompleted, stage)
 }
 
 func TestSwapCreator_Claim_random(t *testing.T) {
-	testClaim(t, ethAssetAddress, 0, defaultSwapValue, nil)
+	testClaim(t, types.EthAssetETH, 0, defaultSwapValue, nil)
 }
 
-func testRefundBeforeT0(t *testing.T, asset ethcommon.Address, erc20Contract *TestERC20, newLogIndex int) {
+func testRefundBeforeT0(t *testing.T, asset types.EthAsset, erc20Contract *TestERC20, newLogIndex int) {
 	// generate refund secret and public key
 	dleq := &dleq.DefaultDLEq{}
 	proof, err := dleq.Prove()
@@ -322,30 +356,34 @@ func testRefundBeforeT0(t *testing.T, asset ethcommon.Address, erc20Contract *Te
 	cmt := res.Secp256k1PublicKey().Keccak256()
 
 	// deploy swap contract with refund key hash
-	auth, conn, pkA := setupXMRTakerAuth(t)
+	pkA := tests.GetTakerTestKey(t)
-	pub := pkA.Public().(*ecdsa.PublicKey)
+	ec, _ := tests.NewEthClient(t)
-	addr := crypto.PubkeyToAddress(*pub)
+	addr := crypto.PubkeyToAddress(pkA.PublicKey)
 
-	address, tx, contract, err := DeploySwapCreator(auth, conn, ethcommon.Address{})
+	swapCreatorAddr, swapCreator := deploySwapCreator(t, ec, pkA)
-	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
-	require.NoError(t, err)
-	t.Logf("gas cost to deploy SwapCreator.sol: %d", receipt.GasUsed)
 
-	if asset != ethAssetAddress {
+	if asset.IsToken() {
-		approveERC20(t, auth, conn, erc20Contract, address, defaultSwapValue)
+		approveERC20(t, ec, pkA, erc20Contract, swapCreatorAddr, defaultSwapValue)
 	}
 
-	nonce := big.NewInt(0)
+	txOpts := getAuth(t, pkA)
-	auth.Value = defaultSwapValue
+	txOpts.Value = defaultSwapValue
-	tx, err = contract.NewSwap(auth, dummySwapKey, cmt, addr, defaultTimeoutDuration, defaultTimeoutDuration,
-		asset, defaultSwapValue, nonce)
-	require.NoError(t, err)
-	auth.Value = nil
 
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	nonce := GenerateNewSwapNonce()
+	tx, err := swapCreator.NewSwap(txOpts, dummySwapKey, cmt, addr, defaultTimeoutDuration, defaultTimeoutDuration,
+		asset.Address(), defaultSwapValue, nonce)
 	require.NoError(t, err)
-	t.Logf("gas cost to call new_swap: %d", receipt.GasUsed)
+
+	receipt := getReceipt(t, ec, tx)
+	if asset.IsETH() {
+		t.Logf("gas cost to call ETH NewSwap: %d (delta %d)",
+			receipt.GasUsed, MaxNewSwapETHGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxNewSwapETHGas, int(receipt.GasUsed), "ETH NewSwap")
+	} else {
+		t.Logf("gas cost to call token NewSwap: %d (delta %d)",
+			receipt.GasUsed, MaxNewSwapTokenGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxNewSwapTokenGas, int(receipt.GasUsed), "ETH NewSwap")
+	}
 
 	require.Equal(t, newLogIndex+1, len(receipt.Logs))
 	id, err := GetIDFromLog(receipt.Logs[newLogIndex])
@@ -361,28 +399,38 @@ func testRefundBeforeT0(t *testing.T, asset ethcommon.Address, erc20Contract *Te
 		PubKeyRefund: cmt,
 		Timeout0:     t0,
 		Timeout1:     t1,
-		Asset:        asset,
+		Asset:        asset.Address(),
 		Value:        defaultSwapValue,
 		Nonce:        nonce,
 	}
 
 	// now let's try to refund
-	tx, err = contract.Refund(auth, swap, proof.Secret())
+	tx, err = swapCreator.Refund(getAuth(t, pkA), swap, proof.Secret())
 	require.NoError(t, err)
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	receipt = getReceipt(t, ec, tx)
-	require.NoError(t, err)
-	t.Logf("gas cost to call Refund: %d", receipt.GasUsed)
 
-	stage, err := contract.Swaps(nil, id)
+	if asset.IsETH() {
+		t.Logf("gas cost to call ETH Refund: %d (delta %d)",
+			receipt.GasUsed, MaxRefundETHGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxRefundETHGas, int(receipt.GasUsed), "ETH Refund")
+	} else {
+		t.Logf("gas cost to call token Refund: %d (delta %d)",
+			receipt.GasUsed, MaxRefundTokenGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxRefundTokenGas, int(receipt.GasUsed), "Token Refund")
+	}
+
+	stage, err := swapCreator.Swaps(nil, id)
 	require.NoError(t, err)
 	require.Equal(t, StageCompleted, stage)
 }
 
 func TestSwapCreator_Refund_beforeT0(t *testing.T) {
-	testRefundBeforeT0(t, ethAssetAddress, nil, 0)
+	testRefundBeforeT0(t, types.EthAssetETH, nil, 0)
 }
 
-func testRefundAfterT1(t *testing.T, asset ethcommon.Address, erc20Contract *TestERC20, newLogIndex int) {
+func testRefundAfterT1(t *testing.T, asset types.EthAsset, erc20Contract *TestERC20, newLogIndex int) {
+	ctx := context.Background()
+
 	// generate refund secret and public key
 	dleq := &dleq.DefaultDLEq{}
 	proof, err := dleq.Prove()
@@ -394,31 +442,35 @@ func testRefundAfterT1(t *testing.T, asset ethcommon.Address, erc20Contract *Tes
 	cmt := res.Secp256k1PublicKey().Keccak256()
 
 	// deploy swap contract with refund key hash
-	auth, conn, pkA := setupXMRTakerAuth(t)
+	pkA := tests.GetTakerTestKey(t)
-	pub := pkA.Public().(*ecdsa.PublicKey)
+	ec, _ := tests.NewEthClient(t)
-	addr := crypto.PubkeyToAddress(*pub)
+	addr := crypto.PubkeyToAddress(pkA.PublicKey)
 
-	address, tx, contract, err := DeploySwapCreator(auth, conn, ethcommon.Address{})
+	swapCreatorAddr, swapCreator := deploySwapCreator(t, ec, pkA)
-	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
-	require.NoError(t, err)
-	t.Logf("gas cost to deploy SwapCreator.sol: %d", receipt.GasUsed)
 
-	if asset != ethAssetAddress {
+	if asset.IsToken() {
-		approveERC20(t, auth, conn, erc20Contract, address, defaultSwapValue)
+		approveERC20(t, ec, pkA, erc20Contract, swapCreatorAddr, defaultSwapValue)
 	}
 
-	nonce := big.NewInt(0)
+	txOpts := getAuth(t, pkA)
-	timeout := big.NewInt(3)
+	txOpts.Value = defaultSwapValue
-	auth.Value = defaultSwapValue
-	tx, err = contract.NewSwap(auth, dummySwapKey, cmt, addr, timeout, timeout,
-		asset, defaultSwapValue, nonce)
-	require.NoError(t, err)
-	auth.Value = nil
 
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	nonce := GenerateNewSwapNonce()
+	timeout := big.NewInt(3)
+	tx, err := swapCreator.NewSwap(txOpts, dummySwapKey, cmt, addr, timeout, timeout,
+		asset.Address(), defaultSwapValue, nonce)
 	require.NoError(t, err)
-	t.Logf("gas cost to call new_swap: %d", receipt.GasUsed)
+	receipt := getReceipt(t, ec, tx)
+
+	if asset.IsETH() {
+		t.Logf("gas cost to call ETH NewSwap: %d (delta %d)",
+			receipt.GasUsed, MaxNewSwapETHGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxNewSwapETHGas, int(receipt.GasUsed), "ETH NewSwap")
+	} else {
+		t.Logf("gas cost to call token NewSwap: %d (delta %d)",
+			receipt.GasUsed, MaxNewSwapTokenGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxNewSwapTokenGas, int(receipt.GasUsed), "Token NewSwap")
+	}
 
 	require.Equal(t, newLogIndex+1, len(receipt.Logs))
 	id, err := GetIDFromLog(receipt.Logs[newLogIndex])
@@ -436,53 +488,50 @@ func testRefundAfterT1(t *testing.T, asset ethcommon.Address, erc20Contract *Tes
 		PubKeyRefund: cmt,
 		Timeout0:     t0,
 		Timeout1:     t1,
-		Asset:        asset,
+		Asset:        asset.Address(),
 		Value:        defaultSwapValue,
 		Nonce:        nonce,
 	}
 
 	secret := proof.Secret()
-	tx, err = contract.Refund(auth, swap, secret)
+	tx, err = swapCreator.Refund(getAuth(t, pkA), swap, secret)
 	require.NoError(t, err)
-	_, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	_, err = block.WaitForReceipt(ctx, ec, tx.Hash())
 	require.ErrorContains(t, err, "VM Exception while processing transaction: revert")
 
 	<-time.After(time.Until(time.Unix(t1.Int64()+1, 0)))
 
 	// now let's try to refund
-	tx, err = contract.Refund(auth, swap, secret)
+	tx, err = swapCreator.Refund(getAuth(t, pkA), swap, secret)
 	require.NoError(t, err)
-	receipt, err = block.WaitForReceipt(context.Background(), conn, tx.Hash())
+	receipt = getReceipt(t, ec, tx)
-	require.NoError(t, err)
-	t.Logf("gas cost to call Refund: %d", receipt.GasUsed)
 
-	callOpts := &bind.CallOpts{
+	if asset.IsETH() {
-		From:    crypto.PubkeyToAddress(*pub),
+		t.Logf("gas cost to call ETH Refund: %d (delta %d)",
-		Context: context.Background(),
+			receipt.GasUsed, MaxRefundETHGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxRefundETHGas, int(receipt.GasUsed), "ETH Refund")
+	} else {
+		t.Logf("gas cost to call token Refund: %d (delta %d)",
+			receipt.GasUsed, MaxRefundTokenGas-int(receipt.GasUsed))
+		require.GreaterOrEqual(t, MaxRefundTokenGas, int(receipt.GasUsed), "Token Refund")
 	}
 
-	stage, err := contract.Swaps(callOpts, id)
+	callOpts := &bind.CallOpts{Context: ctx}
+	stage, err := swapCreator.Swaps(callOpts, id)
 	require.NoError(t, err)
 	require.Equal(t, StageCompleted, stage)
 }
 
 func TestSwapCreator_Refund_afterT1(t *testing.T) {
-	testRefundAfterT1(t, ethAssetAddress, nil, 0)
+	testRefundAfterT1(t, types.EthAssetETH, nil, 0)
 }
 
-func TestSwapCreator_MultipleSwaps(t *testing.T) {
 // test case where contract has multiple swaps happening at once
-	conn, chainID := tests.NewEthClient(t)
+func TestSwapCreator_MultipleSwaps(t *testing.T) {
-
 	pkContractCreator := tests.GetTestKeyByIndex(t, 0)
-	auth, err := bind.NewKeyedTransactorWithChainID(pkContractCreator, chainID)
+	ec, _ := tests.NewEthClient(t)
-	require.NoError(t, err)
 
-	_, tx, contract, err := DeploySwapCreator(auth, conn, ethcommon.Address{})
+	_, swapCreator := deploySwapCreator(t, ec, pkContractCreator)
-	require.NoError(t, err)
-	receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
-	require.NoError(t, err)
-	t.Logf("gas cost to deploy SwapCreator.sol: %d", receipt.GasUsed)
 
 	const numSwaps = 16
 	type swapCase struct {
@@ -493,12 +542,6 @@ func TestSwapCreator_MultipleSwaps(t *testing.T) {
 		swap      SwapCreatorSwap
 	}
 
-	getAuth := func(sc *swapCase) *bind.TransactOpts {
-		auth, err := bind.NewKeyedTransactorWithChainID(sc.walletKey, chainID)
-		require.NoError(t, err)
-		return auth
-	}
-
 	swapCases := [numSwaps]swapCase{}
 
 	// setup all swap instances
@@ -539,25 +582,26 @@ func TestSwapCreator_MultipleSwaps(t *testing.T) {
 	for i := 0; i < numSwaps; i++ {
 		go func(sc *swapCase) {
 			defer wg.Done()
-			auth := getAuth(sc)
+
+			auth := getAuth(t, sc.walletKey)
 			auth.Value = sc.swap.Value
-			tx, err := contract.NewSwap(
+			tx, err := swapCreator.NewSwap(
 				auth,
 				sc.swap.PubKeyClaim,
 				sc.swap.PubKeyRefund,
 				sc.swap.Claimer,
 				defaultTimeoutDuration,
 				defaultTimeoutDuration,
-				ethcommon.Address(types.EthAssetETH),
+				types.EthAssetETH.Address(),
 				sc.swap.Value,
 				sc.swap.Nonce,
 			)
 			require.NoError(t, err)
-			auth.Value = nil
+			receipt := getReceipt(t, ec, tx)
 
-			receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
+			t.Logf("gas cost to call ETH NewSwap[%d]: %d (delta %d)",
-			require.NoError(t, err)
+				sc.index, receipt.GasUsed, MaxNewSwapETHGas-int(receipt.GasUsed))
-			t.Logf("gas cost to call new_swap[%d]: %d", sc.index, receipt.GasUsed)
+			require.GreaterOrEqual(t, MaxNewSwapETHGas, int(receipt.GasUsed), "ETH NewSwap")
 
 			require.Equal(t, 1, len(receipt.Logs))
 			sc.id, err = GetIDFromLog(receipt.Logs[0])
@@ -574,11 +618,12 @@ func TestSwapCreator_MultipleSwaps(t *testing.T) {
 	for i := 0; i < numSwaps; i++ {
 		go func(sc *swapCase) {
 			defer wg.Done()
-			tx, err := contract.SetReady(getAuth(sc), sc.swap)
+			tx, err := swapCreator.SetReady(getAuth(t, sc.walletKey), sc.swap)
 			require.NoError(t, err)
-			receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
+			receipt := getReceipt(t, ec, tx)
-			require.NoError(t, err)
+			t.Logf("gas cost to call SetReady[%d]: %d (delta %d)",
-			t.Logf("gas cost to call SetReady[%d]: %d", sc.index, receipt.GasUsed)
+				sc.index, receipt.GasUsed, MaxSetReadyGas-int(receipt.GasUsed))
+			require.GreaterOrEqual(t, MaxSetReadyGas, int(receipt.GasUsed), "SetReady")
 		}(&swapCases[i])
 	}
 	wg.Wait() // set_ready called on all swaps
@@ -588,11 +633,12 @@ func TestSwapCreator_MultipleSwaps(t *testing.T) {
 	for i := 0; i < numSwaps; i++ {
 		go func(sc *swapCase) {
 			defer wg.Done()
-			tx, err := contract.Claim(getAuth(sc), sc.swap, sc.secret)
+			tx, err := swapCreator.Claim(getAuth(t, sc.walletKey), sc.swap, sc.secret)
 			require.NoError(t, err)
-			receipt, err := block.WaitForReceipt(context.Background(), conn, tx.Hash())
+			receipt := getReceipt(t, ec, tx)
-			require.NoError(t, err)
+			t.Logf("gas cost to call ETH Claim[%d]: %d (delta %d)",
-			t.Logf("gas cost to call Claim[%d]: %d", sc.index, receipt.GasUsed)
+				sc.index, receipt.GasUsed, MaxClaimETHGas-int(receipt.GasUsed))
+			require.GreaterOrEqual(t, MaxClaimETHGas, int(receipt.GasUsed), "ETH Claim")
 		}(&swapCases[i])
 	}
 	wg.Wait() // claim called on all swaps
@@ -602,7 +648,7 @@ func TestSwapCreator_MultipleSwaps(t *testing.T) {
 	for i := 0; i < numSwaps; i++ {
 		go func(sc *swapCase) {
 			defer wg.Done()
-			stage, err := contract.Swaps(nil, sc.id)
+			stage, err := swapCreator.Swaps(nil, sc.id)
 			require.NoError(t, err)
 			require.Equal(t, StageToString(StageCompleted), StageToString(stage))
 		}(&swapCases[i])

ethereum/utils.go

@@ -7,6 +7,7 @@ package contracts
 
 import (
 	"bytes"
+	"crypto/rand"
 	"errors"
 	"fmt"
 	"math/big"
@@ -235,3 +236,12 @@ func GetTimeoutsFromLog(log *ethtypes.Log) (*big.Int, *big.Int, error) {
 	t1 := res[4].(*big.Int)
 	return t0, t1, nil
 }
+
+// GenerateNewSwapNonce generates a random nonce value for use with NewSwap
+// transactions.
+func GenerateNewSwapNonce() *big.Int {
+	u256PlusOne := new(big.Int).Lsh(big.NewInt(1), 256)
+	maxU256 := new(big.Int).Sub(u256PlusOne, big.NewInt(1))
+	n, _ := rand.Int(rand.Reader, maxU256)
+	return n
+}

protocol/xmrmaker/backend_offers.go

@@ -4,7 +4,6 @@
 package xmrmaker
 
 import (
-	"github.com/athanorlabs/atomic-swap/coins"
 	"github.com/athanorlabs/atomic-swap/common/types"
 )
 
@@ -13,17 +12,17 @@ func (inst *Instance) MakeOffer(
 	o *types.Offer,
 	useRelayer bool,
 ) (*types.OfferExtra, error) {
-	// get monero balance
+	err := validateMinBalance(
-	balance, err := inst.backend.XMRClient().GetBalance(0)
+		inst.backend.Ctx(),
+		inst.backend.XMRClient(),
+		inst.backend.ETHClient(),
+		o.MaxAmount,
+		o.EthAsset,
+	)
 	if err != nil {
 		return nil, err
 	}
 
-	unlockedBalance := coins.NewPiconeroAmount(balance.UnlockedBalance).AsMonero()
-	if unlockedBalance.Cmp(o.MaxAmount) <= 0 {
-		return nil, errUnlockedBalanceTooLow{o.MaxAmount, unlockedBalance}
-	}
-
 	if useRelayer && o.EthAsset.IsToken() {
 		return nil, errRelayingWithNonEthAsset
 	}

protocol/xmrmaker/errors.go

@@ -86,3 +86,15 @@ func (e errUnlockedBalanceTooLow) Error() string {
 		e.maxOfferAmount.String(),
 	)
 }
+
+type errETHBalanceTooLowForTokenSwap struct {
+	ethBalance         *apd.Decimal
+	requiredETHToClaim *apd.Decimal
+}
+
+func (e errETHBalanceTooLowForTokenSwap) Error() string {
+	return fmt.Sprintf("balance of %s ETH insufficient for token swap, %s ETH required to claim",
+		e.ethBalance.Text('f'),
+		e.requiredETHToClaim.Text('f'),
+	)
+}

protocol/xmrmaker/min_balance.go

@@ -0,0 +1,66 @@
+package xmrmaker
+
+import (
+	"context"
+	"math/big"
+
+	"github.com/cockroachdb/apd/v3"
+
+	"github.com/athanorlabs/atomic-swap/coins"
+	"github.com/athanorlabs/atomic-swap/common/types"
+	contracts "github.com/athanorlabs/atomic-swap/ethereum"
+	"github.com/athanorlabs/atomic-swap/ethereum/extethclient"
+	"github.com/athanorlabs/atomic-swap/monero"
+)
+
+// validateMinBalance validates that the Maker has sufficient funds to make an
+// XMR for ETH or XMR for token offer.
+func validateMinBalance(
+	ctx context.Context,
+	mc monero.WalletClient,
+	ec extethclient.EthClient,
+	offerMaxAmt *apd.Decimal,
+	ethAsset types.EthAsset,
+) error {
+	piconeroBalance, err := mc.GetBalance(0)
+	if err != nil {
+		return err
+	}
+
+	// Maker needs a sufficient XMR balance regardless if it is an ETH or token swap
+	unlockedBalance := coins.NewPiconeroAmount(piconeroBalance.UnlockedBalance).AsMonero()
+	if unlockedBalance.Cmp(offerMaxAmt) <= 0 {
+		return errUnlockedBalanceTooLow{offerMaxAmt, unlockedBalance}
+	}
+
+	// For a token swap, we also check if the maker has sufficient ETH funds to make a
+	// claim at the end of the swap.
+	if ethAsset.IsToken() {
+		gasPriceWei, err := ec.SuggestGasPrice(ctx)
+		if err != nil {
+			return err
+		}
+
+		requiredETHToClaimTokens := coins.NewWeiAmount(
+			new(big.Int).Mul(big.NewInt(contracts.MaxClaimTokenGas), gasPriceWei),
+		).AsEther()
+
+		weiBalance, err := ec.Balance(ctx)
+		if err != nil {
+			return err
+		}
+
+		ethBalance := weiBalance.AsEther()
+
+		if ethBalance.Cmp(requiredETHToClaimTokens) <= 0 {
+			log.Warnf("Ethereum account has insufficient funds for token claim, balance=%s ETH, required=%s ETH",
+				ethBalance.Text('f'), requiredETHToClaimTokens.Text('f'))
+			return errETHBalanceTooLowForTokenSwap{
+				ethBalance:         ethBalance,
+				requiredETHToClaim: requiredETHToClaimTokens,
+			}
+		}
+	}
+
+	return nil
+}

protocol/xmrmaker/min_balance_test.go

@@ -0,0 +1,59 @@
+package xmrmaker
+
+import (
+	"context"
+	"testing"
+
+	ethcommon "github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/stretchr/testify/require"
+
+	"github.com/athanorlabs/atomic-swap/coins"
+	"github.com/athanorlabs/atomic-swap/common/types"
+	"github.com/athanorlabs/atomic-swap/ethereum/extethclient"
+	"github.com/athanorlabs/atomic-swap/monero"
+	"github.com/athanorlabs/atomic-swap/tests"
+)
+
+func Test_validateMinBalance(t *testing.T) {
+	ctx := context.Background()
+	mc := monero.CreateWalletClient(t)
+	ec := extethclient.CreateTestClient(t, tests.GetMakerTestKey(t))
+	offerMax := coins.StrToDecimal("0.4")
+	tokenAsset := types.EthAsset(ethcommon.Address{0x1}) // arbitrary token asset
+
+	monero.MineMinXMRBalance(t, mc, coins.MoneroToPiconero(offerMax))
+
+	err := validateMinBalance(ctx, mc, ec, offerMax, tokenAsset)
+	require.NoError(t, err)
+}
+
+func Test_validateMinBalance_insufficientXMR(t *testing.T) {
+	ctx := context.Background()
+	ec := extethclient.CreateTestClient(t, tests.GetMakerTestKey(t))
+	mc := monero.CreateWalletClient(t)
+	offerMax := coins.StrToDecimal("0.5")
+
+	// We didn't mine any XMR, so balance is zero
+
+	err := validateMinBalance(ctx, mc, ec, offerMax, types.EthAssetETH)
+	require.ErrorContains(t, err, "balance 0 XMR is too low for maximum offer amount of 0.5 XMR")
+}
+
+func Test_validateMinBalance_insufficientETH(t *testing.T) {
+	ctx := context.Background()
+
+	mc := monero.CreateWalletClient(t)
+	pk, err := crypto.GenerateKey() // new eth key with no balance
+	require.NoError(t, err)
+	ec := extethclient.CreateTestClient(t, pk)
+
+	offerMax := coins.StrToDecimal("0.5")
+	tokenAsset := types.EthAsset(ethcommon.Address{0x1}) // arbitrary token asset
+
+	monero.MineMinXMRBalance(t, mc, coins.MoneroToPiconero(offerMax))
+
+	err = validateMinBalance(ctx, mc, ec, offerMax, tokenAsset)
+	require.Error(t, err)
+	require.Regexp(t, "balance of 0 ETH insufficient for token swap, 0.000\\d+ ETH required to claim", err.Error())
+}

protocol/xmrtaker/errors.go

@@ -31,15 +31,15 @@ var (
 	errInvalidStageForRecovery   = errors.New("cannot create ongoing swap state if stage is not ETHLocked or ContractReady") //nolint:lll
 )
 
-type errAssetBalanceTooLow struct {
+type errTokenBalanceTooLow struct {
-	providedAmount *apd.Decimal
+	providedAmount *apd.Decimal // standard units
-	balance        *apd.Decimal
+	tokenBalance   *apd.Decimal // standard units
 	symbol         string
 }
 
-func (e errAssetBalanceTooLow) Error() string {
+func (e errTokenBalanceTooLow) Error() string {
 	return fmt.Sprintf("balance of %s %s is below provided %s %s",
-		e.balance.Text('f'), e.symbol,
+		e.tokenBalance.Text('f'), e.symbol,
 		e.providedAmount.Text('f'), e.symbol,
 	)
 }
@@ -50,25 +50,37 @@ func errContractAddrMismatch(addr string) error {
 }
 
 type errAmountProvidedTooLow struct {
-	providedAmount *apd.Decimal
+	providedAmtETH *apd.Decimal
-	minAmount      *apd.Decimal
+	offerMinAmtETH *apd.Decimal
 }
 
 func (e errAmountProvidedTooLow) Error() string {
-	return fmt.Sprintf("%s ETH provided is under offer minimum of %s XMR",
+	return fmt.Sprintf("%s ETH provided is under offer minimum of %s ETH",
-		e.providedAmount.String(),
+		e.providedAmtETH.Text('f'),
-		e.minAmount.String(),
+		e.offerMinAmtETH.Text('f'),
 	)
 }
 
 type errAmountProvidedTooHigh struct {
-	providedAmount *apd.Decimal
+	providedAmtETH *apd.Decimal
-	maxAmount      *apd.Decimal
+	offerMaxETH    *apd.Decimal
 }
 
 func (e errAmountProvidedTooHigh) Error() string {
-	return fmt.Sprintf("%s ETH provided is over offer maximum of %s XMR",
+	return fmt.Sprintf("%s ETH provided is over offer maximum of %s ETH",
-		e.providedAmount.String(),
+		e.providedAmtETH.Text('f'),
-		e.maxAmount.String(),
+		e.offerMaxETH.Text('f'),
+	)
+}
+
+type errETHBalanceTooLow struct {
+	currentBalanceETH  *apd.Decimal
+	requiredBalanceETH *apd.Decimal
+}
+
+func (e errETHBalanceTooLow) Error() string {
+	return fmt.Sprintf("balance of %s ETH is under required amount of %s ETH",
+		e.currentBalanceETH.Text('f'),
+		e.requiredBalanceETH.Text('f'),
 	)
 }

protocol/xmrtaker/min_balance.go

@@ -0,0 +1,106 @@
+package xmrtaker
+
+import (
+	"context"
+	"math/big"
+
+	"github.com/cockroachdb/apd/v3"
+
+	"github.com/athanorlabs/atomic-swap/coins"
+	"github.com/athanorlabs/atomic-swap/common/types"
+	contracts "github.com/athanorlabs/atomic-swap/ethereum"
+	"github.com/athanorlabs/atomic-swap/ethereum/extethclient"
+)
+
+// validateMinBalance validates that the Taker has sufficient funds to take an
+// offer
+func validateMinBalance(
+	ctx context.Context,
+	ec extethclient.EthClient,
+	providesAmt *apd.Decimal,
+	asset types.EthAsset,
+) error {
+	gasPrice, err := ec.SuggestGasPrice(ctx)
+	if err != nil {
+		return err
+	}
+
+	weiBalance, err := ec.Balance(ctx)
+	if err != nil {
+		return err
+	}
+
+	if asset.IsETH() {
+		return validateMinBalForETHSwap(weiBalance, providesAmt, gasPrice)
+	}
+
+	tokenBalance, err := ec.ERC20Balance(ctx, asset.Address())
+	if err != nil {
+		return err
+	}
+
+	return validateMinBalForTokenSwap(weiBalance, tokenBalance, providesAmt, gasPrice)
+}
+
+// validateMinBalForETHSwap validates that the Taker has sufficient funds to take an
+// offer of XMR for ETH
+func validateMinBalForETHSwap(weiBalance *coins.WeiAmount, providesAmt *apd.Decimal, gasPriceWei *big.Int) error {
+	providedAmtWei := coins.EtherToWei(providesAmt).BigInt()
+	neededGas := big.NewInt(
+		contracts.MaxNewSwapETHGas +
+			contracts.MaxSetReadyGas +
+			contracts.MaxRefundTokenGas,
+	)
+	neededWeiForGas := new(big.Int).Mul(neededGas, gasPriceWei)
+	neededBalanceWei := new(big.Int).Add(providedAmtWei, neededWeiForGas)
+
+	if weiBalance.BigInt().Cmp(neededBalanceWei) < 0 {
+		log.Warnf("Ethereum account needs additional funds, balance=%s ETH, required=%s ETH",
+			weiBalance.AsEtherString(), coins.NewWeiAmount(neededBalanceWei).AsEtherString())
+		return errETHBalanceTooLow{
+			currentBalanceETH:  weiBalance.AsEther(),
+			requiredBalanceETH: coins.NewWeiAmount(neededBalanceWei).AsEther(),
+		}
+	}
+
+	return nil
+}
+
+// validateMinBalForTokenSwap validates that the Taker has sufficient tokens for
+// to take an XMR->Token swap, and sufficient ETH funds to pay for the gas of
+// the swap.
+func validateMinBalForTokenSwap(
+	weiBalance *coins.WeiAmount,
+	tokenBalance *coins.ERC20TokenAmount,
+	providesAmt *apd.Decimal, // standard units
+	gasPriceWei *big.Int,
+) error {
+	if tokenBalance.AsStandard().Cmp(providesAmt) < 0 {
+		return errTokenBalanceTooLow{
+			providedAmount: providesAmt,
+			tokenBalance:   tokenBalance.AsStandard(),
+			symbol:         tokenBalance.StandardSymbol(),
+		}
+	}
+
+	// For a token swap, we only need an ETH balance to pay for gas. While we
+	// hopefully won't need gas to call refund, we don't want to start the swap
+	// if we don't have enough ETH to call it.
+	neededGas := big.NewInt(contracts.MaxTokenApproveGas +
+		contracts.MaxNewSwapTokenGas +
+		contracts.MaxSetReadyGas +
+		contracts.MaxRefundTokenGas,
+	)
+	neededWeiForGas := new(big.Int).Mul(neededGas, gasPriceWei)
+
+	if weiBalance.BigInt().Cmp(neededWeiForGas) < 0 {
+		log.Warnf("Ethereum account has infufficient balance to pay for gas, balance=%s ETH, required=%s ETH",
+			weiBalance.AsEtherString(), coins.NewWeiAmount(neededWeiForGas).AsEtherString())
+		return errETHBalanceTooLow{
+			currentBalanceETH:  weiBalance.AsEther(),
+			requiredBalanceETH: coins.NewWeiAmount(neededWeiForGas).AsEther(),
+		}
+	}
+
+	return nil
+}

protocol/xmrtaker/min_balance_test.go

@@ -0,0 +1,130 @@
+package xmrtaker
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"math/big"
+	"testing"
+
+	ethcommon "github.com/ethereum/go-ethereum/common"
+	"github.com/stretchr/testify/require"
+
+	"github.com/athanorlabs/atomic-swap/coins"
+	"github.com/athanorlabs/atomic-swap/common/types"
+	contracts "github.com/athanorlabs/atomic-swap/ethereum"
+	"github.com/athanorlabs/atomic-swap/ethereum/block"
+	"github.com/athanorlabs/atomic-swap/ethereum/extethclient"
+	"github.com/athanorlabs/atomic-swap/tests"
+)
+
+func deployTestToken(t *testing.T, ownerKey *ecdsa.PrivateKey) (ethcommon.Address, *coins.ERC20TokenInfo) {
+	ctx := context.Background()
+	ec := extethclient.CreateTestClient(t, ownerKey)
+
+	txOpts, err := ec.TxOpts(ctx)
+	require.NoError(t, err)
+
+	tokenAddr, tx, _, err := contracts.DeployTestERC20(
+		txOpts,
+		ec.Raw(),
+		"Min Max Testing Token",
+		"MMTT",
+		6,
+		ec.Address(),
+		big.NewInt(1000e6), // 1000 standard units
+	)
+	require.NoError(t, err)
+	_, err = block.WaitForReceipt(ctx, ec.Raw(), tx.Hash())
+	require.NoError(t, err)
+
+	tokenInfo, err := ec.ERC20Info(ctx, tokenAddr)
+	require.NoError(t, err)
+
+	return tokenAddr, tokenInfo
+}
+
+func Test_validateMinBalForETHSwap(t *testing.T) {
+	balanceWei := coins.EtherToWei(coins.StrToDecimal("0.5"))
+	providesAmt := coins.StrToDecimal("0.25")
+	gasPriceWei := big.NewInt(35e9) // 35 GWei
+	err := validateMinBalForETHSwap(balanceWei, providesAmt, gasPriceWei)
+	require.NoError(t, err)
+}
+
+func Test_validateMinBalForETHSwap_InsufficientBalance(t *testing.T) {
+	balanceWei := coins.EtherToWei(coins.StrToDecimal("0.5"))
+	providesAmt := balanceWei.AsEther() // provided amount consumes whole balance leaving nothing for gas
+	gasPriceWei := big.NewInt(35e9)     // 35 GWei
+	err := validateMinBalForETHSwap(balanceWei, providesAmt, gasPriceWei)
+	// Amount in check below is truncated, so minor adjustments in the
+	// expected gas won't break the test. The full message looks like:
+	// "balance of 0.5 ETH is under required amount of 0.504541005 ETH"
+	require.ErrorContains(t, err, "balance of 0.5 ETH is under required amount of 0.504")
+}
+
+func Test_validateMinBalForTokenSwap(t *testing.T) {
+	tokenInfo := &coins.ERC20TokenInfo{
+		Address:     ethcommon.Address{0x1},
+		NumDecimals: 6,
+		Name:        "Token",
+		Symbol:      "TK",
+	}
+	balanceWei := coins.EtherToWei(coins.StrToDecimal("0.5"))
+	tokenBalance := coins.NewERC20TokenAmountFromDecimals(coins.StrToDecimal("10"), tokenInfo)
+	providesAmt := coins.StrToDecimal("5")
+	gasPriceWei := big.NewInt(35e9) // 35 GWei
+	err := validateMinBalForTokenSwap(balanceWei, tokenBalance, providesAmt, gasPriceWei)
+	require.NoError(t, err)
+}
+
+func Test_validateMinBalForTokenSwap_InsufficientTokenBalance(t *testing.T) {
+	tokenInfo := &coins.ERC20TokenInfo{
+		Address:     ethcommon.Address{0x1},
+		NumDecimals: 6,
+		Name:        "Token",
+		Symbol:      "TK",
+	}
+	balanceWei := coins.EtherToWei(coins.StrToDecimal("0.5"))
+	tokenBalance := coins.NewERC20TokenAmountFromDecimals(coins.StrToDecimal("10"), tokenInfo)
+	providesAmt := coins.StrToDecimal("20")
+	gasPriceWei := big.NewInt(35e9) // 35 GWei
+	err := validateMinBalForTokenSwap(balanceWei, tokenBalance, providesAmt, gasPriceWei)
+	require.ErrorContains(t, err, `balance of 10 "TK" is below provided 20 "TK"`)
+}
+
+func Test_validateMinBalForTokenSwap_InsufficientETHBalance(t *testing.T) {
+	tokenInfo := &coins.ERC20TokenInfo{
+		Address:     ethcommon.Address{0x1},
+		NumDecimals: 6,
+		Name:        "Token",
+		Symbol:      "TK",
+	}
+	balanceWei := coins.EtherToWei(coins.StrToDecimal("0.007"))
+	tokenBalance := coins.NewERC20TokenAmountFromDecimals(coins.StrToDecimal("10"), tokenInfo)
+	providesAmt := coins.StrToDecimal("1")
+	gasPriceWei := big.NewInt(35e9) // 35 GWei
+	err := validateMinBalForTokenSwap(balanceWei, tokenBalance, providesAmt, gasPriceWei)
+	// Amount in check below is truncated, so minor adjustments in the
+	// expected gas won't break the test. The full message looks like:
+	// "balance of 0.007 ETH is under required amount of 0.00743302 ETH"
+	require.ErrorContains(t, err, `balance of 0.007 ETH is under required amount of 0.0074`)
+}
+
+func Test_validateMinBalanceETH(t *testing.T) {
+	ctx := context.Background()
+	pk := tests.GetTakerTestKey(t)
+	ec := extethclient.CreateTestClient(t, pk)
+	providesAmt := coins.StrToDecimal("0.3") // ganache taker key will have more than this
+	err := validateMinBalance(ctx, ec, providesAmt, types.EthAssetETH)
+	require.NoError(t, err)
+}
+
+func Test_validateMinBalanceToken(t *testing.T) {
+	ctx := context.Background()
+	pk := tests.GetTakerTestKey(t)
+	ec := extethclient.CreateTestClient(t, pk)
+	tokenAddr, _ := deployTestToken(t, pk)
+	providesAmt := coins.StrToDecimal("1") // less than the 1k tokens belonging to the taker
+	err := validateMinBalance(ctx, ec, providesAmt, types.EthAsset(tokenAddr))
+	require.NoError(t, err)
+}

protocol/xmrtaker/net.go

@@ -32,17 +32,32 @@ func (inst *Instance) InitiateProtocol(
 		return nil, err
 	}
 
-	expectedAmount, err := offer.ExchangeRate.ToXMR(providesAmount)
+	offerMinETH, err := offer.ExchangeRate.ToETH(offer.MinAmount)
 	if err != nil {
 		return nil, err
 	}
 
-	if expectedAmount.Cmp(offer.MinAmount) < 0 {
+	offerMaxETH, err := offer.ExchangeRate.ToETH(offer.MaxAmount)
-		return nil, errAmountProvidedTooLow{providesAmount, offer.MinAmount}
+	if err != nil {
+		return nil, err
 	}
 
-	if expectedAmount.Cmp(offer.MaxAmount) > 0 {
+	if offerMinETH.Cmp(providesAmount) > 0 {
-		return nil, errAmountProvidedTooHigh{providesAmount, offer.MaxAmount}
+		return nil, errAmountProvidedTooLow{providesAmount, offerMinETH}
+	}
+
+	if offerMaxETH.Cmp(providesAmount) < 0 {
+		return nil, errAmountProvidedTooHigh{providesAmount, offerMaxETH}
+	}
+
+	err = validateMinBalance(
+		inst.backend.Ctx(),
+		inst.backend.ETHClient(),
+		providesAmount,
+		offer.EthAsset,
+	)
+	if err != nil {
+		return nil, err
 	}
 
 	providedAmount, err := pcommon.GetEthAssetAmount(
@@ -55,8 +70,7 @@ func (inst *Instance) InitiateProtocol(
 		return nil, err
 	}
 
-	state, err := inst.initiate(makerPeerID, providedAmount, coins.MoneroToPiconero(expectedAmount),
+	state, err := inst.initiate(makerPeerID, providedAmount, offer.ExchangeRate, offer.EthAsset, offer.ID)
-		offer.ExchangeRate, offer.EthAsset, offer.ID)
 	if err != nil {
 		return nil, err
 	}
@@ -67,7 +81,6 @@ func (inst *Instance) InitiateProtocol(
 func (inst *Instance) initiate(
 	makerPeerID peer.ID,
 	providesAmount coins.EthAssetAmount,
-	expectedAmount *coins.PiconeroAmount,
 	exchangeRate *coins.ExchangeRate,
 	ethAsset types.EthAsset,
 	offerID types.Hash,
@@ -79,44 +92,12 @@ func (inst *Instance) initiate(
 		return nil, errProtocolAlreadyInProgress
 	}
 
-	ethBalance, err := inst.backend.ETHClient().Balance(inst.backend.Ctx())
-	if err != nil {
-		return nil, err
-	}
-
-	// Ensure the user's balance is strictly greater than the amount they will provide
-	if ethAsset.IsETH() && ethBalance.Cmp(providesAmount.(*coins.WeiAmount)) <= 0 {
-		log.Warnf("Account %s needs additional funds for swap balance=%s ETH providesAmount=%s ETH",
-			inst.backend.ETHClient().Address(), ethBalance.AsEtherString(), providesAmount.AsStandard())
-		return nil, errAssetBalanceTooLow{
-			providedAmount: providesAmount.AsStandard(),
-			balance:        ethBalance.AsEther(),
-			symbol:         "ETH",
-		}
-	}
-
-	if ethAsset.IsToken() {
-		tokenBalance, err := inst.backend.ETHClient().ERC20Balance(inst.backend.Ctx(), ethAsset.Address()) //nolint:govet
-		if err != nil {
-			return nil, err
-		}
-
-		if tokenBalance.AsStandard().Cmp(providesAmount.AsStandard()) <= 0 {
-			return nil, errAssetBalanceTooLow{
-				providedAmount: providesAmount.AsStandard(),
-				balance:        tokenBalance.AsStandard(),
-				symbol:         tokenBalance.StandardSymbol(),
-			}
-		}
-	}
-
 	s, err := newSwapStateFromStart(
 		inst.backend,
 		makerPeerID,
 		offerID,
 		inst.noTransferBack,
 		providesAmount,
-		expectedAmount,
 		exchangeRate,
 		ethAsset,
 	)

protocol/xmrtaker/swap_state.go

@@ -7,7 +7,6 @@ package xmrtaker
 
 import (
 	"context"
-	"crypto/rand"
 	"errors"
 	"fmt"
 	"math/big"
@@ -101,7 +100,6 @@ func newSwapStateFromStart(
 	offerID types.Hash,
 	noTransferBack bool,
 	providedAmount coins.EthAssetAmount,
-	expectedAmount *coins.PiconeroAmount,
 	exchangeRate *coins.ExchangeRate,
 	ethAsset types.EthAsset,
 ) (*swapState, error) {
@@ -123,12 +121,17 @@ func newSwapStateFromStart(
 		return nil, err
 	}
 
+	expectedAmount, err := exchangeRate.ToXMR(providedAmount.AsStandard())
+	if err != nil {
+		return nil, err
+	}
+
 	info := pswap.NewInfo(
 		makerPeerID,
 		offerID,
 		coins.ProvidesETH,
 		providedAmount.AsStandard(),
-		expectedAmount.AsMonero(),
+		expectedAmount,
 		exchangeRate,
 		ethAsset,
 		stage,
@@ -562,7 +565,7 @@ func (s *swapState) lockAsset() (*ethtypes.Receipt, error) {
 
 	log.Debugf("locking %s %s in contract", providedAmt.AsStandard(), providedAmt.StandardSymbol())
 
-	nonce := generateNonce()
+	nonce := contracts.GenerateNewSwapNonce()
 	receipt, err := s.sender.NewSwap(
 		cmtXMRMaker,
 		cmtXMRTaker,
@@ -698,10 +701,3 @@ func (s *swapState) refund() (*ethtypes.Receipt, error) {
 func generateKeys() (*pcommon.KeysAndProof, error) {
 	return pcommon.GenerateKeysAndProof()
 }
-
-func generateNonce() *big.Int {
-	u256PlusOne := new(big.Int).Lsh(big.NewInt(1), 256)
-	maxU256 := new(big.Int).Sub(u256PlusOne, big.NewInt(1))
-	n, _ := rand.Int(rand.Reader, maxU256)
-	return n
-}

protocol/xmrtaker/swap_state_test.go

@@ -135,10 +135,9 @@ func newBackend(t *testing.T) backend.Backend {
 func newTestSwapStateAndNet(t *testing.T) (*swapState, *mockNet) {
 	b, net := newBackendAndNet(t)
 	providedAmt := coins.EtherToWei(coins.StrToDecimal("1"))
-	expectedAmt := coins.MoneroToPiconero(coins.StrToDecimal("1"))
 	exchangeRate := coins.ToExchangeRate(coins.StrToDecimal("1.0")) // 100%
 	swapState, err := newSwapStateFromStart(b, testPeerID, types.Hash{}, true,
-		providedAmt, expectedAmt, exchangeRate, types.EthAssetETH)
+		providedAmt, exchangeRate, types.EthAssetETH)
 	require.NoError(t, err)
 	return swapState, net
 }
@@ -187,9 +186,8 @@ func newTestSwapStateWithERC20(t *testing.T, providesAmt *apd.Decimal) (*swapSta
 	providesEthAssetAmt := coins.NewERC20TokenAmountFromDecimals(providesAmt, tokenInfo)
 
 	exchangeRate := coins.ToExchangeRate(apd.New(1, 0)) // 100%
-	zeroPiconeros := coins.NewPiconeroAmount(0)
 	swapState, err := newSwapStateFromStart(b, testPeerID, types.Hash{}, false,
-		providesEthAssetAmt, zeroPiconeros, exchangeRate, types.EthAsset(addr))
+		providesEthAssetAmt, exchangeRate, types.EthAsset(addr))
 	require.NoError(t, err)
 	return swapState, contract
 }

relayer/claim_request.go

@@ -7,13 +7,11 @@ package relayer
 import (
 	"context"
 	"crypto/ecdsa"
-	"math/big"
 
 	ethcommon "github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/ethclient"
 	logging "github.com/ipfs/go-log"
 
-	"github.com/athanorlabs/atomic-swap/coins"
 	contracts "github.com/athanorlabs/atomic-swap/ethereum"
 	"github.com/athanorlabs/atomic-swap/net/message"
 )
@@ -23,12 +21,6 @@ const (
 	forwarderClaimGas = 156000 // worst case gas usage when using forwarder to claim
 )
 
-// FeeWei and FeeEth are the fixed 0.009 ETH fee for using a swap relayer to claim.
-var (
-	FeeWei = big.NewInt(9e15)
-	FeeEth = coins.NewWeiAmount(FeeWei).AsEther()
-)
-
 var log = logging.Logger("relayer")
 
 // CreateRelayClaimRequest fills and returns a RelayClaimRequest ready for

relayer/forwarder.go

@@ -16,6 +16,7 @@ import (
 	ethcrypto "github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethclient"
 
+	"github.com/athanorlabs/atomic-swap/coins"
 	contracts "github.com/athanorlabs/atomic-swap/ethereum"
 )
 
@@ -74,7 +75,7 @@ func createForwarderRequest(
 	secret *[32]byte,
 ) (*gsnforwarder.IForwarderForwardRequest, error) {
 
-	calldata, err := getClaimRelayerTxCalldata(FeeWei, swap, secret)
+	calldata, err := getClaimRelayerTxCalldata(coins.RelayerFeeWei, swap, secret)
 	if err != nil {
 		return nil, err
 	}

relayer/submit_transaction_test.go

@@ -60,7 +60,7 @@ func Test_ValidateAndSendTransaction(t *testing.T) {
 	require.NoError(t, err)
 	receipt, err := block.WaitForReceipt(ctx, ec.Raw(), tx.Hash())
 	require.NoError(t, err)
-	t.Logf("gas cost to call new_swap: %d", receipt.GasUsed)
+	require.GreaterOrEqual(t, contracts.MaxNewSwapETHGas, int(receipt.GasUsed))
 	txOpts.Value = big.NewInt(0)
 
 	logIndex := 0 // change to 2 for ERC20, but ERC20 swaps cannot use the relayer
@@ -87,8 +87,8 @@ func Test_ValidateAndSendTransaction(t *testing.T) {
 	tx, err = swapCreator.SetReady(txOpts, *swap)
 	require.NoError(t, err)
 	receipt, err = block.WaitForReceipt(ctx, ec.Raw(), tx.Hash())
-	t.Logf("gas cost to call SetReady: %d", receipt.GasUsed)
 	require.NoError(t, err)
+	require.GreaterOrEqual(t, contracts.MaxSetReadyGas, int(receipt.GasUsed))
 
 	secret := proof.Secret()
 

relayer/validate.go

@@ -65,9 +65,9 @@ func validateClaimValues(
 	}
 
 	// The relayer fee must be strictly less than the swap value
-	if FeeWei.Cmp(request.Swap.Value) >= 0 {
+	if coins.RelayerFeeWei.Cmp(request.Swap.Value) >= 0 {
 		return fmt.Errorf("swap value of %s ETH is too low to support %s ETH relayer fee",
-			coins.FmtWeiAsETH(request.Swap.Value), coins.FmtWeiAsETH(FeeWei))
+			coins.FmtWeiAsETH(request.Swap.Value), coins.FmtWeiAsETH(coins.RelayerFeeWei))
 	}
 
 	return nil

relayer/validate_test.go

@@ -14,6 +14,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/stretchr/testify/require"
 
+	"github.com/athanorlabs/atomic-swap/coins"
 	"github.com/athanorlabs/atomic-swap/common/types"
 	contracts "github.com/athanorlabs/atomic-swap/ethereum"
 	"github.com/athanorlabs/atomic-swap/net/message"
@@ -35,17 +36,17 @@ func TestValidateRelayerFee(t *testing.T) {
 	testCases := []testCase{
 		{
 			description: "swap value equal to relayer fee",
-			value:       FeeWei,
+			value:       coins.RelayerFeeWei,
 			expectErr:   "swap value of 0.009 ETH is too low to support 0.009 ETH relayer fee",
 		},
 		{
 			description: "swap value less than relayer fee",
-			value:       new(big.Int).Sub(FeeWei, big.NewInt(1e15)),
+			value:       new(big.Int).Sub(coins.RelayerFeeWei, big.NewInt(1e15)),
 			expectErr:   "swap value of 0.008 ETH is too low to support 0.009 ETH relayer fee",
 		},
 		{
 			description: "swap value larger than min fee",
-			value:       new(big.Int).Add(FeeWei, big.NewInt(1e15)),
+			value:       new(big.Int).Add(coins.RelayerFeeWei, big.NewInt(1e15)),
 		},
 	}
 

tests/integration_test.go

@@ -187,7 +187,7 @@ func (s *IntegrationTestSuite) testSuccessOneSwap(asset types.EthAsset, useRelay
 	defer cancel()
 
 	bwsc := s.newSwapdWSClient(ctx, defaultXMRMakerSwapdWSEndpoint)
-	min := coins.StrToDecimal("0.1")
+	min := coins.StrToDecimal("0.2")
 	offerResp, statusCh, err := bwsc.MakeOfferAndSubscribe(min, xmrmakerProvideAmount,
 		exchangeRate, asset, useRelayer)
 	require.NoError(s.T(), err)
@@ -529,7 +529,7 @@ func (s *IntegrationTestSuite) testAbortXMRTakerCancels(asset types.EthAsset) {
 
 	bwsc := s.newSwapdWSClient(ctx, defaultXMRMakerSwapdWSEndpoint)
 
-	min := coins.StrToDecimal("0.1")
+	min := coins.StrToDecimal("0.2")
 	offerResp, statusCh, err := bwsc.MakeOfferAndSubscribe(min, xmrmakerProvideAmount,
 		exchangeRate, asset, false)
 	require.NoError(s.T(), err)