Returnvalue.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "forge-std/Test.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

interface USDT {
  function transfer(address to, uint256 value) external;

  function balanceOf(address account) external view returns (uint256);

  function approve(address spender, uint256 value) external;
}
interface CheatCodes {
    function startPrank(address) external;
    function stopPrank() external;
    function createSelectFork(string calldata,uint256) external returns(uint256);
}

contract ContractTest is DSTest {
    using SafeERC20 for IERC20;
    IERC20 constant usdt = IERC20(0xdAC17F958D2ee523a2206206994597C13D831ec7);
    CheatCodes cheats = CheatCodes(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D);


  function setUp() public {
    cheats.createSelectFork("mainnet", 16138254); 
  }
        
function testTransfer() public {
    cheats.startPrank(0xef0DCc839c1490cEbC7209BAa11f46cfe83805ab);
    usdt.transfer(address(this),123);
    cheats.stopPrank();
    }

function testSafeTransfer() public {
    cheats.startPrank(0xef0DCc839c1490cEbC7209BAa11f46cfe83805ab);
    usdt.safeTransfer(address(this),123);
    cheats.stopPrank();
    }

receive() payable external{}

}