fix: insert tolerance into redeemShare() checks [SUP-8853]

src/router-plus/SuperformRouterPlus.sol

@@ -27,6 +27,9 @@ contract SuperformRouterPlus is ISuperformRouterPlus, BaseSuperformRouterPlus {
 
     uint256 public ROUTER_PLUS_PAYLOAD_ID;
 
+    /// @dev Tolerance constant to account for tokens with rounding issues on transfer
+    uint256 constant TOLERANCE_CONSTANT = 2 wei;
+
     //////////////////////////////////////////////////////////////
     //                      CONSTRUCTOR                         //
     //////////////////////////////////////////////////////////////
@@ -521,6 +524,7 @@ contract SuperformRouterPlus is ISuperformRouterPlus, BaseSuperformRouterPlus {
         if (
             (balanceDifference != assets)
                 || (ENTIRE_SLIPPAGE * assets < ((expectedOutputAmount_ * (ENTIRE_SLIPPAGE - maxSlippage_))))
+                || (assets - TOLERANCE_CONSTANT > balanceDifference)
         ) {
             revert ASSETS_RECEIVED_OUT_OF_SLIPPAGE();
         }

test/unit/router-plus/SuperformRouterPlus.t.sol

@@ -553,6 +553,54 @@ contract SuperformRouterPlusTest is ProtocolActions {
         SuperformRouterPlus(ROUTER_PLUS_SOURCE).deposit4626{ value: 1 ether }(address(mockVault), args);
     }
 
+    function test_deposit4626_withinTolerance() public {
+        vm.startPrank(deployer);
+
+        // Deploy a mock ERC4626 vault
+        VaultMock mockVault = new VaultMock(IERC20(getContract(SOURCE_CHAIN, "DAI")), "Mock Vault", "mVLT");
+
+        // Mint some DAI to the deployer
+        uint256 daiAmount = 1e18 - 2 wei;
+
+        // Approve and deposit DAI into the mock vault
+        MockERC20(getContract(SOURCE_CHAIN, "DAI")).approve(address(mockVault), daiAmount);
+        uint256 vaultTokenAmount = mockVault.deposit(daiAmount, deployer);
+
+        // Prepare deposit4626 args
+        ISuperformRouterPlus.Deposit4626Args memory args = ISuperformRouterPlus.Deposit4626Args({
+            amount: vaultTokenAmount,
+            expectedOutputAmount: daiAmount, // Assuming 1:1 ratio for simplicity
+            maxSlippage: 100, // 1%
+            receiverAddressSP: deployer,
+            depositCallData: _buildDepositCallData(superformId1, daiAmount)
+        });
+
+        // Approve RouterPlus to spend vault tokens
+        mockVault.approve(ROUTER_PLUS_SOURCE, vaultTokenAmount);
+
+        // Execute deposit4626
+        vm.recordLogs();
+        SuperformRouterPlus(ROUTER_PLUS_SOURCE).deposit4626{ value: 1 ether }(address(mockVault), args);
+
+        // Verify the results
+        assertGt(
+            SuperPositions(SUPER_POSITIONS_SOURCE).balanceOf(deployer, superformId1),
+            0,
+            "Superform balance should be greater than 0"
+        );
+
+        // Check that the vault tokens were transferred from the deployer
+        assertEq(mockVault.balanceOf(deployer), 0, "Deployer's vault token balance should be 0");
+
+        // Check that the RouterPlus contract doesn't hold any tokens
+        assertEq(mockVault.balanceOf(ROUTER_PLUS_SOURCE), 0, "RouterPlus should not hold any vault tokens");
+        assertEq(
+            MockERC20(getContract(SOURCE_CHAIN, "DAI")).balanceOf(ROUTER_PLUS_SOURCE),
+            0,
+            "RouterPlus should not hold any DAI"
+        );
+    }
+
     function test_rebalanceSinglePosition_errors() public {
         vm.startPrank(deployer);