Add regular send at the end of each TC for fast transfer (#18365)

* Add regular send at the end of each TC for fast transfer

* Use contract directly as helper is not thread safe

Author: carte7000

integration-tests/smoke/ccip/ccip_fast_transfer_test.go

@@ -22,6 +22,7 @@ import (
 
 	chainselectors "github.com/smartcontractkit/chain-selectors"
 
+	"github.com/smartcontractkit/chainlink-ccip/chains/evm/gobindings/generated/v1_2_0/router"
 	"github.com/smartcontractkit/chainlink-ccip/chains/evm/gobindings/generated/v1_5_0/rmn_contract"
 	"github.com/smartcontractkit/chainlink-ccip/chains/evm/gobindings/generated/v1_5_1/token_pool"
 	cldf_chain "github.com/smartcontractkit/chainlink-deployments-framework/chain"
@@ -89,7 +90,7 @@ type fastTransferE2ETestCase struct {
 var (
 	initialFillerTokenAmountOnDest = big.NewInt(0).Mul(big.NewInt(1e18), big.NewInt(1000))
 	initialUserTokenAmountOnSource = big.NewInt(200000)
-	defaultEthAmount               = big.NewInt(0).Mul(big.NewInt(params.Ether), big.NewInt(1000))
+	defaultEthAmount               = big.NewInt(0).Mul(big.NewInt(params.Ether), big.NewInt(10000))
 	transferAmount                 = big.NewInt(100000)
 	expectedFastTransferFee        = big.NewInt(100)
 	tokenDecimals                  = uint8(18)
@@ -1239,6 +1240,50 @@ func runFastTransferTestCase(t *testing.T, ctx *fastTransferTestContext, tc *fas
 		runAssertions(t, sourceToken, destinationToken, fillerAddress, tc.postRegularTransferFillerAssertions, "Post Regular Transfer Filler Assertions")
 		runAssertions(t, sourceToken, destinationToken, userAddress, tc.postRegularTransferUserAssertions, "Post Regular Transfer User Assertions")
 		runAssertions(t, sourceToken, destinationToken, destinationTokenPoolAddress, tc.postRegularTransferPoolAssertions, "Post Regular Transfer Pool Assertions")
+
+		if !tc.expectNoExecutionError {
+			ctx.env.Logger.Info("Sanity check regular token transfer (slow-path)")
+			// We want to ensure regular transfer works as expected
+			message := router.ClientEVM2AnyMessage{
+				Receiver: common.LeftPadBytes(userAddress.Bytes(), 32),
+				Data:     []byte{},
+				TokenAmounts: []router.ClientEVMTokenAmount{
+					{
+						Token:  sourceToken.Address(),
+						Amount: initialUserTokenAmountOnSource,
+					},
+				},
+				FeeToken:  common.HexToAddress("0x0"),
+				ExtraArgs: nil,
+			}
+			userBalance, err := destinationToken.BalanceOf(nil, userAddress)
+			require.NoError(t, err)
+			// Top-up user account on source chain
+			fundAccountWithToken(t, ctx.SourceChain(), userAddress, sourceMinter, initialUserTokenAmountOnSource, ctx.sourceLock)
+			approveToken(t, ctx.SourceChain(), userTransactor(), sourceToken, ctx.sourceChainState.Router.Address(), ctx.sourceLock)
+			func() {
+				ctx.sendLock.Lock()
+				defer ctx.sendLock.Unlock()
+				seqNum, err = ctx.sequenceNumberRetriever(nil, ctx.DestinationChainSelector())
+				require.NoError(t, err)
+				router := onChainState.Chains[ctx.SourceChainSelector()].Router
+				fee, err := router.GetFee(&bind.CallOpts{Context: context.Background()}, ctx.DestinationChainSelector(), message)
+				require.NoError(t, err)
+				userTransac := userTransactor()
+				userTransac.Value = fee
+				tx, err := router.CcipSend(userTransac, ctx.DestinationChainSelector(), message)
+				require.NoError(t, err)
+				ctx.env.Logger.Infof("Sending regular transfer transaction: %s", tx.Hash().Hex())
+				_, err = ctx.SourceChain().Confirm(tx)
+				require.NoError(t, err)
+			}()
+
+			ctx.waitForExecution(t, seqNum)
+			finalBalance, err := destinationToken.BalanceOf(nil, userAddress)
+			require.NoError(t, err)
+			expectedBalance := new(big.Int).Add(userBalance, initialUserTokenAmountOnSource)
+			require.Equal(t, expectedBalance.String(), finalBalance.String(), "Final balance after regular transfer does not match expected value")
+		}
 	})
 }