feat: add additional estimateAdditionalCost view function

src/apps/mock/IncentivizedMockEscrow.sol

@@ -30,6 +30,11 @@ contract IncentivizedMockEscrow is IncentivizedMessageEscrow, Ownable2Step {
         amount = costOfMessages;
     }
 
+    function estimateAdditionalCost(bytes32 /* destinationChainIdentifier */) external view returns(address asset, uint256 amount) {
+        asset =  address(0);
+        amount = costOfMessages;
+    }
+
     function collectPayments() external {
         unchecked {
             payable(owner()).transfer(accumulator - 1);

src/apps/mock/OnRecvIncentivizedMockEscrow.sol

@@ -38,6 +38,11 @@ contract OnRecvIncentivizedMockEscrow is IncentivizedMessageEscrow {
         amount = 0;
     }
 
+    function estimateAdditionalCost(bytes32 /* destinationChainIdentifier */) external pure returns(address asset, uint256 amount) {
+        asset =  address(0);
+        amount = 0;
+    }
+
     function _proofValidPeriod(bytes32 /* destinationIdentifier */) override internal pure returns(uint64) {
         return 0;
     }

src/apps/polymer/APolymerEscrow.sol

@@ -25,6 +25,11 @@ abstract contract APolymerEscrow is IncentivizedMessageEscrow {
         amount = 0;
     }
 
+    function estimateAdditionalCost(bytes32 /* destinationChainIdentifier */) external pure returns(address asset, uint256 amount) {
+        asset =  address(0);
+        amount = 0;
+    }
+
     function _uniqueSourceIdentifier() internal view override returns (bytes32 sourceIdentifier) {
         return sourceIdentifier = bytes32(block.chainid);
     }

src/apps/wormhole/IncentivizedWormholeEscrow.sol

@@ -45,6 +45,11 @@ contract IncentivizedWormholeEscrow is IncentivizedMessageEscrow, WormholeVerifi
         amount = WORMHOLE.messageFee();
     }
 
+    function estimateAdditionalCost(bytes32 /* destinationChainIdentifier */) external view returns(address asset, uint256 amount) {
+        asset =  address(0);
+        amount = WORMHOLE.messageFee();
+    }
+
     /** @notice Wormhole proofs are valid until the guardian set is changed. The new guradian set may sign a new VAA */
     function _proofValidPeriod(bytes32 /* destinationIdentifier */) override internal pure returns(uint64) {
         return 0;

src/interfaces/IIncentivizedMessageEscrow.sol

@@ -36,6 +36,14 @@ interface IIncentivizedMessageEscrow is IMessageEscrowStructs, IMessageEscrowErr
      * @return amount The number of assets to pay.
      */
     function estimateAdditionalCost() external view returns(address asset, uint256 amount);
+
+    /**
+     * @notice Estimates the additional cost to the messaging router to validate the message
+     * @param destinationChainIdentifier Destination chain. Some messaging protocols have chain based costs.
+     * @return asset The asset the token is in. If native token, returns address(0);
+     * @return amount The number of assets to pay.
+     */
+    function estimateAdditionalCost(bytes32 destinationChainIdentifier) external view returns(address asset, uint256 amount);
 
     function timeoutMessage(
         bytes32 sourceIdentifier,

test/IncentivizedMessageEscrow/processMessage/Reentry.call.t.sol

@@ -61,7 +61,7 @@ contract CallReentryTest is TestCommon, ICrossChainReceiver {
                 messageIdentifier,
                 _DESTINATION_ADDRESS_APPLICATION,
                 feeRecipient,
-                uint48(0xfcb6),  // Gas used
+                uint48(0xfccc),  // Gas used
                 uint64(1),
                 uint8(1)
             )

test/layerzero/TestLZMisc.t.sol

@@ -40,6 +40,6 @@ contract TestLZMisc is LZCommon {
             address(layerZeroEscrow),
             abi.encodeCall(layerZeroEscrow.getFee, (remoteEid, address(layerZeroEscrow), 0, hex""))
         );
-        layerZeroEscrow.estimateAdditionalCost(remoteEid);
+        layerZeroEscrow.estimateAdditionalCost(bytes32(uint256(remoteEid)));
     }
 }