test: coverage for SuccinctFeeVault (#271)

contracts/src/payments/SuccinctFeeVault.sol

@@ -4,6 +4,7 @@ pragma solidity ^0.8.16;
 import {IFeeVault} from "./interfaces/IFeeVault.sol";
 import {TimelockedUpgradeable} from "../upgrades/TimelockedUpgradeable.sol";
 import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
 
 /// @title SuccinctFeeVault
 /// @author Succinct Labs
@@ -18,24 +19,15 @@ import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 ///         make a bulk deposit.
 /// @dev Address(0) is used to represent native currency in places where token address is specified.
 contract SuccinctFeeVault is IFeeVault, TimelockedUpgradeable {
+    using SafeERC20 for IERC20;
+
     /// @notice Tracks the amount of active balance that an account has for Succinct services.
     /// @dev balances[token][account] returns the amount of balance for token the account has. To
     ///      check native currency balance, use address(0) as the token address.
     mapping(address => mapping(address => uint256)) public balances;
     /// @notice The allowed senders for the deduct functions.
     mapping(address => bool) public allowedDeductors;
 
-    event Received(address indexed account, address indexed token, uint256 amount);
-    event Deducted(address indexed account, address indexed token, uint256 amount);
-    event Collected(address indexed to, address indexed token, uint256 amount);
-
-    error InvalidAccount(address account);
-    error InvalidToken(address token);
-    error InsufficentAllowance(address token, uint256 amount);
-    error InsufficientBalance(address token, uint256 amount);
-    error FailedToSendNative(uint256 amount);
-    error OnlyDeductor(address sender);
-
     modifier onlyDeductor() {
         if (!allowedDeductors[msg.sender]) {
             revert OnlyDeductor(msg.sender);
@@ -94,7 +86,7 @@ contract SuccinctFeeVault is IFeeVault, TimelockedUpgradeable {
             revert InsufficentAllowance(_token, _amount);
         }
 
-        token.transferFrom(msg.sender, address(this), _amount);
+        token.safeTransferFrom(msg.sender, address(this), _amount);
         balances[_token][_account] += _amount;
 
         emit Received(_account, _token, _amount);
@@ -168,4 +160,8 @@ contract SuccinctFeeVault is IFeeVault, TimelockedUpgradeable {
 
         emit Collected(_to, _token, _amount);
     }
+
+    /// @dev This empty reserved space to add new variables without shifting down storage.
+    ///      See: https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
+    uint256[50] private __gap;
 }

contracts/src/payments/interfaces/IFeeVault.sol

@@ -1,22 +1,23 @@
 // SPDX-License-Identifier: MIT
 pragma solidity ^0.8.16;
 
-interface IFeeVault {
-    /// @notice Returns the amount of active balance that an account has.
-    /// @param token The address of the token to check the balance of. To check native currency
-    ///        balance, use address(0) as the token address.
-    /// @param account The address of the account to check the balance of.
-    function balances(address token, address account) external view returns (uint256);
+interface IFeeVaultEvents {
+    event Received(address indexed account, address indexed token, uint256 amount);
+    event Deducted(address indexed account, address indexed token, uint256 amount);
+    event Collected(address indexed to, address indexed token, uint256 amount);
+}
 
-    /// @notice Deposit the specified amount of native currency from the caller.
-    /// @dev The native currency is represented by address(0) in balances.
-    /// @param account The account to deposit the native currency for.
-    function depositNative(address account) external payable;
+interface IFeeVaultErrors {
+    error InvalidAccount(address account);
+    error InvalidToken(address token);
+    error InsufficentAllowance(address token, uint256 amount);
+    error InsufficientBalance(address token, uint256 amount);
+    error FailedToSendNative(uint256 amount);
+    error OnlyDeductor(address sender);
+}
 
-    /// @notice Deposit the specified amount of the specified token from the caller.
-    /// @dev MUST approve this contract to spend at least `amount` of `token` before calling this.
-    /// @param account The account to deposit the tokens to.
-    /// @param token The address of the token to deposit.
-    /// @param amount The amount of the token to deposit.
+interface IFeeVault is IFeeVaultEvents, IFeeVaultErrors {
+    function balances(address token, address account) external view returns (uint256);
+    function depositNative(address account) external payable;
     function deposit(address account, address token, uint256 amount) external;
 }