Lesson10: why we write vm.prank in setUp function before ourToken.transfer?

[codeplay22]

When i don't type vm.prank(msg.sender) in setUp function this error comes, but when i check the balance of address(this) it's 79228162414264337593543950335 which is much higher than STARTING_BALANCE which is 100 ether and if i also check the balance of transfer function in ERC20 Which is coming out to be 79228162414264337593543950335 only still it's giving me ERC20InsufficientBalance (you can see it in the image down below). Why this error is coming? it should not come because owner have balance of 79228162414264337593543950335 which is much higher than 100 ethers, so it should tranfer it??

This is my setUp function

        deployer = new DeployOurToken();
        ourToken = deployer.run();
        console.log("address of address(this) in OurTokenTest.t.sol is", address(this));
        console.log("msg.sender balance is", msg.sender.balance);
        console.log("address(this).balance", address(this).balance - (STARTING_BALANCE));
        ourToken.transfer(bob, STARTING_BALANCE);
    }

[EngrPips]

Hello @codeplay22, Please show your full setup function.

[codeplay22]

hi @EngrPips
this is it

function setUp() public {
        deployer = new DeployOurToken();
        ourToken = deployer.run();
        console.log("address of address(this) in OurTokenTest.t.sol is", address(this));
        // vm.prank(address(msg.sender));
        console.log("msg.sender balance is", msg.sender.balance);
        console.log("address(this).balance", address(this).balance - (STARTING_BALANCE));
        // console.log("balanceof(address(this))", balanceof(address(this)));
        ourToken.transfer(bob, STARTING_BALANCE);
    }

[EngrPips]

Good. Please show DeployOurToken and ourToken files.

[codeplay22]

DeployOurToken.s.sol

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity ^0.8.18;

import {Script} from "forge-std/Script.sol";
import {OurToken} from "../src/OurToken.sol";
import {console} from "forge-std/Test.sol";

contract DeployOurToken is Script {
    uint256 public constant INITIAL_SUPPLY = 1000 ether;

    function run() external returns (OurToken) {
        vm.startBroadcast();
        OurToken ot = new OurToken(INITIAL_SUPPLY);
        // console.log("address(this) in DeployOurToken.s.sol is",address(this));
        // console.log("address of ot is",address(ot));
        // console.log("msg.sender is in DeployOurToken.s.sol is",msg.sender);
        vm.stopBroadcast();
        return ot;
    }
}

ManualToken.sol

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity ^0.8.18;

contract ManualToken {

    mapping (address => uint256) private s_balance;

    function name() public pure returns (string memory){
        return "Manual Token";
    }

    function balanceOf(address _owner) public view  returns (uint256 balance){
        return s_balance[_owner];
    }

    function decimals() public pure returns (uint8){
        return 18;
    }

    function totalSupply() public pure returns (uint256) {
        return 100 ether;//100000000000
    }

    function transfer(address _to, uint256 _amount) public {
        uint256 previousBalances = balanceOf(msg.sender) + balanceOf(_to);
        s_balance[msg.sender] -= _amount;
        s_balance[_to] += _amount;
        require(balanceOf(msg.sender) + balanceOf(_to) == previousBalances); 
    }





}

OurToken.sol

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity ^0.8.18;
import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import {console} from "forge-std/Test.sol";
contract OurToken is ERC20{

    constructor(uint256 initialSupply) ERC20("OurToken","OT"){
        _mint(msg.sender,initialSupply);
        console.log("address(this) inside OurToken.sol is",address(this));
        console.log("msg.sender in OurToken.sol is",msg.sender);
    }    

}

[EngrPips]

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity ^0.8.18;

import {Script} from "forge-std/Script.sol";
import {OurToken} from "../src/OurToken.sol";
import {console} from "forge-std/Test.sol";

contract DeployOurToken is Script {
    uint256 public constant INITIAL_SUPPLY = 1000 ether;

    function run() external returns (OurToken) {
        vm.startBroadcast(); <@ here
        OurToken ot = new OurToken(INITIAL_SUPPLY);
        // console.log("address(this) in DeployOurToken.s.sol is",address(this));
        // console.log("address of ot is",address(ot));
        // console.log("msg.sender is in DeployOurToken.s.sol is",msg.sender);
        vm.stopBroadcast();
        return ot;
    }
}

So, in this deployer script, you used vm.startBroadcast() and did not pass in a privateKey, so that will make foundry use its default privateKey. Take note of this, as you will need to understand the next code.

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity ^0.8.18;
import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import {console} from "forge-std/Test.sol";
contract OurToken is ERC20{

    constructor(uint256 initialSupply) ERC20("OurToken","OT"){
        _mint(msg.sender,initialSupply); <@ here
        console.log("address(this) inside OurToken.sol is",address(this));
        console.log("msg.sender in OurToken.sol is",msg.sender);
    }    

}

So in your OurToken contract, you mint initialSupply amount of OurToken to the msg.sender, which will be the default foundry sender because you did not pass in any privateKey when you used vm.startBroadcast() in your deployment script.

function setUp() public {
        deployer = new DeployOurToken();
        ourToken = deployer.run();
        console.log("address of address(this) in OurTokenTest.t.sol is", address(this));
        // vm.prank(address(msg.sender));
        console.log("msg.sender balance is", msg.sender.balance);
        console.log("address(this).balance", address(this).balance - (STARTING_BALANCE));
        // console.log("balanceof(address(this))", balanceof(address(this)));
        ourToken.transfer(bob, STARTING_BALANCE); <@ here
    }

So here you are trying to transfer token from the test script to bob, but the test did not have any balance on OurToken because the initialSupply was minted to foundry default sender. So your test reverts with ERC20InsufficientBalance. If anything is confusing, please ask question

[codeplay22]

@EngrPips
i did'nt understand the last part which is this
the test did not have any balance on OurToken because the initialSupply was minted to foundry default sender.

can you explain those lines more deeply and easily?, i think i didnt understand that english.

did you mean that we didnt use test to mint initialSupply inside the constructor?

[EngrPips]

I mean, your token will mint to the foundry default sender address because of the vm.startBroadcast(), which you didn't pass any private key to

constructor(uint256 initialSupply) ERC20("OurToken","OT"){
        _mint(msg.sender,initialSupply); <@ here
        console.log("address(this) inside OurToken.sol is",address(this));
        console.log("msg.sender in OurToken.sol is",msg.sender);
    }    

This line _mint(msg.sender,initialSupply); <@ here mints to the foundry default sender, but in your test file, it is the test address that is trying to send token to bob. The test address does not hold any token, so the test reverted with. ERC20InsufficientBalance. If anything is confusing, please ask question

[codeplay22]

okay,
so how can i check token of msg.sender then?

[EngrPips]

How do you mean check token of msg.sender? can you please explain in a more simple way?

[EngrPips]

deployer = new DeployOurToken();
        ourToken = deployer.run();
        console.log("address of address(this) in OurTokenTest.t.sol is", address(this));
        console.log("msg.sender balance is", msg.sender.balance);
        console.log("address(this).balance", address(this).balance - (STARTING_BALANCE));
        console.log("The balance of this contract is: , ourToken.balanceOf(address(this)));
        ourToken.transfer(bob, STARTING_BALANCE);
    }

Run this code, and it should print the ourToken balance of your test contract.

[EngrPips]

Please ask questions if anything is still confusing.

[codeplay22]

@EngrPips thanks u for your help
so basically it's not mapped to msg.sender's address that's why it's giving me insufficient balance because i didn't mint token with address(this) address so that's why its giving balance of 0 because test's address(address(this)) not mapped to any token(balance).
your explaination was a bit confusing to me but still your code helped me to thinking about it and got to this.
So thanks a lot!!

[EngrPips]

I am very sorry that I explained things poorly. I tried to do the best I could. I am glad you at least figured it out. Keep crushing it, buddy.

[codeplay22]

no worries
Thanks a lot! you too!

[EngrPips]

I appreciate you, Man.