test: add SwapExactSyForYtTest

test/unit/SwapExactSyForYt.t.sol

@@ -1,6 +1,29 @@
 /// SPDX-License-Identifier: UNLICENSED
 pragma solidity ^0.8.13;
 
+import {ERC20} from "solmate/tokens/ERC20.sol";
+import {PYIndexLib, IPYieldToken, PYIndex} from "pendle/core/StandardizedYield/PYIndex.sol";
 import {SetUp} from "../SetUp.sol";
 
-contract SwapExactSyForYtTest is SetUp {}
+contract SwapExactSyForYtTest is SetUp {
+    using PYIndexLib for IPYieldToken;
+
+    function test_swapExactSyForYt_TransfersTokens() public initSYPool {
+        address to = address(0xbeef);
+
+        deal(address(SY), address(this), 1 ether);
+        uint256 preSYBalance = ERC20(address(SY)).balanceOf(address(this));
+        uint256 preYTBalance = ERC20(address(YT)).balanceOf(to);
+        uint256 preSYBalanceRMM = ERC20(address(SY)).balanceOf(address(rmm));
+
+        uint256 amountIn = 1 ether;
+
+        PYIndex index = YT.newIndex();
+        uint256 ytOut = rmm.computeSYToYT(index, 1 ether, block.timestamp, 500 ether);
+        (uint256 amountOut,) = rmm.swapExactSyForYt(ytOut, 0, address(to));
+
+        assertEq(ERC20(address(SY)).balanceOf(address(this)), preSYBalance - amountIn);
+        assertEq(ERC20(address(YT)).balanceOf(to), preYTBalance + amountOut);
+        assertEq(ERC20(address(SY)).balanceOf(address(rmm)), preSYBalanceRMM + amountIn);
+    }
+}