add MessageTransferTest contract for testing message transfer functionality

Author: cqlyj

test/MessageTransferTest.t.sol

@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.26;
+
+import {Test} from "forge-std/Test.sol";
+import {CCIPLocalSimulator, IRouterClient, LinkToken} from "@chainlink/local/src/ccip/CCIPLocalSimulator.sol";
+import {SepoliaSender} from "src/SepoliaSender.sol";
+import {AmoyReceiver} from "src/AmoyReceiver.sol";
+
+contract MessageTransferTest is Test {
+    CCIPLocalSimulator public ccipLocalSimulator;
+    uint64 public destinationChainSelector;
+
+    SepoliaSender public sepoliaSender;
+    AmoyReceiver public amoyReceiver;
+
+    address public USER = makeAddr("USER");
+
+    function setUp() public {
+        ccipLocalSimulator = new CCIPLocalSimulator();
+
+        (
+            uint64 chainSelector,
+            IRouterClient sourceRouter,
+            IRouterClient destinationRouter,
+            ,
+            LinkToken link,
+            ,
+
+        ) = ccipLocalSimulator.configuration();
+
+        destinationChainSelector = chainSelector;
+
+        sepoliaSender = new SepoliaSender(address(sourceRouter), address(link));
+        amoyReceiver = new AmoyReceiver(address(destinationRouter));
+    }
+
+    function testMessageTransferWithLinkTokenPaid() public {
+        ccipLocalSimulator.requestLinkFromFaucet(
+            address(sepoliaSender),
+            5 ether
+        );
+
+        bytes memory signedMessage = abi.encodePacked("Hello, Amoy!");
+
+        bytes32 messageId = sepoliaSender.sendMessage(
+            destinationChainSelector,
+            address(amoyReceiver),
+            signedMessage
+        );
+
+        bytes memory receivedMessage = amoyReceiver.getSignedMessage();
+        bytes32 lastMessageId = amoyReceiver.getMessageId();
+
+        string memory expectedMessage = "Hello, Amoy!";
+        string memory actualMessage = abi.decode(receivedMessage, (string));
+
+        assertEq(messageId, lastMessageId);
+        assertEq(expectedMessage, actualMessage);
+    }
+}