Build a contract that lets me lock my erc-20 tokens somewhere.

Call the function BridgeETH (BridgeETH.sol)

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { console } from "forge-std/console.sol";
import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";

contract BridgeETH is Ownable {
    uint256 public balance;
    address public tokenAddress;

    mapping(address => uint256) public pendingBalance;

    constructor(address _tokenAddress) Ownable(msg.sender) {
        tokenAddress = _tokenAddress;
    }

    function deposit(IERC20 _tokenAddress, uint256 _amount) public {
        require(address(_tokenAddress) == tokenAddress);
        require(_tokenAddress.allowance(msg.sender, address(this)) >= _amount);
        require(_tokenAddress.transferFrom(msg.sender, address(this), _amount));
        pendingBalance[msg.sender] += _amount;
    }

    function withdraw(IERC20 _tokenAddress, uint256 _amount) public {
        require(pendingBalance[msg.sender] >= _amount);
        pendingBalance[msg.sender] -= _amount;
        _tokenAddress.transfer(msg.sender, _amount);
    }
}

Also create an ERC20 token that you create that you need to lock (USDT.sol)

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { console } from "forge-std/console.sol";
import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";

contract USDT is ERC20, Ownable {
    constructor() ERC20("USDT", "USDT") Ownable(msg.sender) {

    }

    function mint(address _to, uint256 _amount) public onlyOwner {
        _mint(_to, _amount);
    }
}

Write tests for it (BridgeETH.t.sol)

// SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.13;

import "forge-std/Test.sol";

import "src/BridgeETH.sol";
import "src/USDT.sol";
import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract BridgeETHTest is Test {
    event Transfer(address indexed from, address indexed to, uint256 value);

    BridgeETH bridge;
    USDT usdt;

    function setUp() public {
        usdt = new USDT();
        bridge = new BridgeETH(address(usdt));
    }

    function test_Deposit() public {
        usdt.mint(0x2966473D85A76A190697B5b9b66b769436EFE8e5, 200);
        vm.startPrank(0x2966473D85A76A190697B5b9b66b769436EFE8e5);
        usdt.approve(address(bridge), 200);

        bridge.deposit(usdt, 200);
        assertEq(usdt.balanceOf(0x2966473D85A76A190697B5b9b66b769436EFE8e5), 0);
        assertEq(usdt.balanceOf(address(bridge)), 200);

        bridge.withdraw(usdt, 100);

        assertEq(usdt.balanceOf(0x2966473D85A76A190697B5b9b66b769436EFE8e5), 100);
        assertEq(usdt.balanceOf(address(bridge)), 100);

    }


}