Foundry dealing custom ERC20

ERC20.t.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.10;

import "../../lib/ds-test/src/test.sol";
import "../../lib/forge-std/src/Vm.sol";
import "../../lib/forge-std/src/Test.sol";

interface ERC20 {
    function totalSupply() external view returns (uint);
    function balanceOf(address tokenOwner) external view returns (uint balance);
    function allowance(address tokenOwner, address spender) external view returns (uint remaining);
    function transfer(address to, uint tokens) external returns (bool success);
    function approve(address spender, uint tokens) external returns (bool success);
    function transferFrom(address from, address to, uint tokens) external returns (bool success);

    function symbol() external view returns (string memory);
    function name() external view returns (string memory);
    function decimals() external view returns (uint8);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
} 

contract ContractTest is DSTest, Test {
    ERC20 private WETH = ERC20(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);
    address emptyWallet = address(3);

    function setUp() public {}

    function testExample() public {
        assertTrue(true);
    }

    function testEmptyWallet() public {
        require(WETH.balanceOf(emptyWallet) == 0);
    }

    function testDeal() public {
        deal(address(WETH), emptyWallet, 1000 ether);
        require(WETH.balanceOf(emptyWallet) > 0);
    }
}