Solidity – Withdraw Fails in Foundry Test: Common Issues and Fixes

forgefoundrysolidity

I want to test a function that I have written for my smart contract with Forge from Foundry.

This is the function that allows to withdraw the Ether in this contract.

function withdraw() public onlyOwner {
        address _owner = owner();
        uint256 amount = address(this).balance;
        (bool sent, ) = _owner.call{value: amount}(
            "Revenue from NFT Sale"
        );
        require(sent, "Failed to send Ether");
    }

When I write a test case it fails for the withdrawal part, but I cannot see why

function testWithdrawExample() public {
        // owner of the contract is just the default account
        // which is the deployer of the test contract
        // => deployer = address(this);
        // ... prepare state

        // execute function
        cryptoDevs.withdraw();
 
        // ... assert state
    }

All what I see when I use high verbosity (traces visible)

├─ [7845] CryptoDevs::withdraw() 
    │   ├─ [190] CryptoDevsTest::52657665{value: 200000000000000000}(6e75652066726f6d204e46542043727970746f20446576732053616c65) 
    │   │   └─ ← ()
    │   └─ ← "Failed to send Ether"
    └─ ← "Failed to send Ether"

Best Answer

When you want to withdraw and the signing account is the deployer and test contract itself (it's the same), like you have, then you need to give the contract TestContract is Test the ability to receive ether, like you would do for any other contract. Add the following to the contracts body.

// Function to receive Ether. msg.data must be empty
receive() external payable {}

// Fallback function is called when msg.data is not empty
fallback() external payable {}

Other than that you could use vm.prank and specify an EOA which is capable of receiving ether anyway. Remember you would need to use vm.prank for contract deployment (owner is not test contract but EOA and before withdraw function execution)

Related Solutions

How to Withdraw Ether from a Contract

The function would be something like this:

pragma solidity >=0.8.0;

function withdraw() {
    payable(msg.sender).transfer(address(this).balance);
}

Just make sure you only allow yourself to access it

solidity – How to Withdraw Amount from Deployed Ethereum Contract

In your case, when you call stealAmntFromContract_method1() method inside WithrawAmtFromAnotherContract the msg.sender value passed to withdraw() function inside ReceiveEther is the WithrawAmtFromAnotherContract smart contract address and for this reason you see this error. That's because, WithrawAmtFromAnotherContract call withdraw() function on your behalf and passed it its address like msg.sender. You must to change your smart contract in this way:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;

contract ReceiveEther {

    receive() external payable {}
    fallback() external payable {}

    function getBalance() public view returns (uint) {
        return address(this).balance;
    }

    function withdraw(address _to) public payable{
        payable(address(_to)).transfer(address(this).balance);
    }
}

contract SendEther {

    function sendViaCall(address payable _to) public payable {
        // Call returns a boolean value indicating success or failure.
        // This is the current recommended method to use.
        (bool sent,) = _to.call{value: msg.value}("");
        require(sent, "Failed to send Ether");
    }
}

interface With {
    function getBalance() external view returns(uint);
    function withdraw(address _to) external payable;
}

contract WithrawAmtFromAnotherContract{

    function getBalance(address _address) public view returns(uint){
        return With(_address).getBalance();
    }

    function stealAmntFromContract_method1(address _address) public {
        With(_address).withdraw(msg.sender);
    }
}

In this smart contract, I added a new input parameter call _to (datatype: address) that allows you to keep the user address that call stealAmntFromContract_method1 and pass it to widthdraw() function. At this point, this last function'll have inside _to input parameter the user address and it can transfer your balance to him.

NOTE: I also changed withdraw() signature in With interface.

Best Answer

Related Solutions

How to Withdraw Ether from a Contract

solidity – How to Withdraw Amount from Deployed Ethereum Contract

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