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// SPDX-License-Identifier: MIT pragma solidity ^0.8.18; import "forge-std/console.sol"; interface Token { /// @param _owner The address from which the balance will be retrieved /// @return balance the balance function balanceOf(address _owner) external view returns (uint256 balance); /// @notice send `_value` token to `_to` from `msg.sender` /// @param _to The address of the recipient /// @param _value The amount of token to be transferred /// @return success Whether the transfer was successful or not function transfer( address _to, uint256 _value ) external returns (bool success); /// @notice send `_value` token to `_to` from `_from` on the condition it is approved by `_from` /// @param _from The address of the sender /// @param _to The address of the recipient /// @param _value The amount of token to be transferred /// @return success Whether the transfer was successful or not function transferFrom( address _from, address _to, uint256 _value ) external returns (bool success); /// @notice `msg.sender` approves `_addr` to spend `_value` tokens /// @param _spender The address of the account able to transfer the tokens /// @param _value The amount of wei to be approved for transfer /// @return success Whether the approval was successful or not function approve( address _spender, uint256 _value ) external returns (bool success); /// @param _owner The address of the account owning tokens /// @param _spender The address of the account able to transfer the tokens /// @return remaining Amount of remaining tokens allowed to spent function allowance( address _owner, address _spender ) external view returns (uint256 remaining); event Transfer(address indexed _from, address indexed _to, uint256 _value); event Approval( address indexed _owner, address indexed _spender, uint256 _value ); } contract Standard_Token is Token { uint256 private constant MAX_UINT256 = 2 ** 256 - 1; mapping(address => uint256) public balances; mapping(address => mapping(address => uint256)) public allowed; uint256 public totalSupply; /* NOTE: The following variables are OPTIONAL vanities. One does not have to include them. They allow one to customise the token contract & in no way influences the core functionality. Some wallets/interfaces might not even bother to look at this information. */ string public name; //fancy name: eg Simon Bucks uint8 public decimals; //How many decimals to show. string public symbol; //An identifier: eg SBX constructor( uint256 _initialAmount, string memory _tokenName, uint8 _decimalUnits, string memory _tokenSymbol ) { balances[msg.sender] = _initialAmount; // Give the creator all initial tokens totalSupply = _initialAmount; // Update total supply name = _tokenName; // Set the name for display purposes decimals = _decimalUnits; // Amount of decimals for display purposes symbol = _tokenSymbol; // Set the symbol for display purposes } function transfer( address _to, uint256 _value ) public override returns (bool success) { require( balances[msg.sender] >= _value, "token balance is lower than the value requested" ); balances[msg.sender] -= _value; balances[_to] += _value; emit Transfer(msg.sender, _to, _value); //solhint-disable-line indent, no-unused-vars return true; } function transferFrom( address _from, address _to, uint256 _value ) public override returns (bool success) { uint256 allowance = allowed[_from][msg.sender]; require( balances[_from] >= _value && allowance >= _value, "token balance or allowance is lower than amount requested" ); balances[_to] += _value; balances[_from] -= _value; if (allowance < MAX_UINT256) { allowed[_from][msg.sender] -= _value; } emit Transfer(_from, _to, _value); //solhint-disable-line indent, no-unused-vars return true; } function balanceOf( address _owner ) public view override returns (uint256 balance) { return balances[_owner]; } function approve( address _spender, uint256 _value ) public override returns (bool success) { allowed[msg.sender][_spender] = _value; emit Approval(msg.sender, _spender, _value); //solhint-disable-line indent, no-unused-vars return true; } function allowance( address _owner, address _spender ) public view override returns (uint256 remaining) { return allowed[_owner][_spender]; } function mintToken(address _to, uint _amount) public { balances[_to] += _amount; } } contract Payment { function transferERC20( address _token, address _to, uint256 _amount ) public { Token(_token).transferFrom(msg.sender, _to, _amount); } } //////////////////////////////////////////// Test // SPDX-License-Identifier: MIT pragma solidity ^0.8.18; import {Test, Vm} from "forge-std/Test.sol"; import "forge-std/console.sol"; import {Standard_Token, Payment} from "../src/HelloWorld.sol"; contract testSample is Test { Standard_Token public _Standard_Token; Payment public _Payment; address private immutable SELLER = address(1); address private constant BUYER = address(2); function setUp() public { _Standard_Token = new Standard_Token(0, "Token", 18, "Token"); _Payment = new Payment(); _Standard_Token.mintToken(SELLER, 10e18); } function testTransfer(address, address, uint) public { // console user balance console.log( "balance of SELLER before", _Standard_Token.balanceOf(SELLER) ); // vm setup to seller account vm.startPrank(SELLER); // TX1, Approve _Standard_Token.approve(address(_Payment), 5e18); // TX2, Transfer _Payment.transferERC20(address(_Standard_Token), address(0), 5e18); console.log( "balance of SELLER after", _Standard_Token.balanceOf(SELLER) ); } }