refactor(StakeManager): add custom StakeManager__FundsLocked error

.gas-snapshot

@@ -7,5 +7,6 @@ MigrateTest:test_RevertWhen_SenderIsNotVault() (gas: 10629)
 StakeManagerTest:testDeployment() (gas: 26172)
 StakeTest:testDeployment() (gas: 26172)
 StakeTest:test_RevertWhen_SenderIsNotVault() (gas: 10638)
-UnstakeTest:testDeployment() (gas: 26172)
-UnstakeTest:test_RevertWhen_SenderIsNotVault() (gas: 10575)
+UnstakeTest:testDeployment() (gas: 26355)
+UnstakeTest:test_RevertWhen_FundsLocked() (gas: 973435)
+UnstakeTest:test_RevertWhen_SenderIsNotVault() (gas: 10609)

contracts/StakeManager.sol

@@ -7,8 +7,8 @@ import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
 import { StakeVault } from "./StakeVault.sol";
 
 contract StakeManager is Ownable {
-
     error StakeManager__SenderIsNotVault();
+    error StakeManager__FundsLocked();
 
     struct Account {
         uint256 lockUntil;
@@ -75,7 +75,9 @@ contract StakeManager is Ownable {
      */
     function unstake(uint256 _amount) external onlyVault {
         Account storage account = accounts[msg.sender];
-        require(account.lockUntil <= block.timestamp, "Funds are locked");
+        if (account.lockUntil > block.timestamp) {
+            revert StakeManager__FundsLocked();
+        }
         processAccount(account, currentEpoch);
         uint256 reducedMultiplier = (_amount * account.multiplier) / account.balance;
         account.multiplier -= reducedMultiplier;

test/StakeManager.t.sol

@@ -1,17 +1,21 @@
 // SPDX-License-Identifier: UNLICENSED
 pragma solidity ^0.8.19;
 
+import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+
 import { Test } from "forge-std/Test.sol";
 import { Deploy } from "../script/Deploy.s.sol";
 import { DeploymentConfig } from "../script/DeploymentConfig.s.sol";
 import { StakeManager } from "../contracts/StakeManager.sol";
+import { StakeVault } from "../contracts/StakeVault.sol";
 
 contract StakeManagerTest is Test {
     DeploymentConfig internal deploymentConfig;
     StakeManager internal stakeManager;
 
     address internal stakeToken;
     address internal deployer;
+    address internal testUser = makeAddr("testUser");
 
     function setUp() public virtual {
         Deploy deployment = new Deploy();
@@ -29,6 +33,14 @@ contract StakeManagerTest is Test {
         assertEq(address(stakeManager.oldManager()), address(0));
         assertEq(stakeManager.totalSupply(), 0);
     }
+
+    function _createTestVault(address owner) internal returns (StakeVault vault) {
+        vm.prank(owner);
+        vault = new StakeVault(owner, ERC20(stakeToken), stakeManager);
+
+        vm.prank(deployer);
+        stakeManager.setVault(address(vault).codehash);
+    }
 }
 
 contract StakeTest is StakeManagerTest {
@@ -51,6 +63,21 @@ contract UnstakeTest is StakeManagerTest {
         vm.expectRevert(StakeManager.StakeManager__SenderIsNotVault.selector);
         stakeManager.unstake(100);
     }
+
+    function test_RevertWhen_FundsLocked() public {
+        // ensure user has funds
+        deal(stakeToken, testUser, 1000);
+        StakeVault userVault = _createTestVault(testUser);
+
+        vm.startPrank(testUser);
+        ERC20(stakeToken).approve(address(userVault), 100);
+
+        uint256 lockTime = 1 days;
+        userVault.stake(100, lockTime);
+
+        vm.expectRevert(StakeManager.StakeManager__FundsLocked.selector);
+        userVault.unstake(100);
+    }
 }
 
 contract LockTest is StakeManagerTest {