Lesson 7: FAILED tests/test_lottery_unit.py::test_can_pick_winner_correctly - AttributeError: Contract 'VRFCoordinatorMock' object has no attribute 'callbackWithRandomness'

[pbelouin-mpiwg]

Hello everyone,

I'm having an error when running the test_can_pick_winner correctly, which I've pasted in the title:

AttributeError: Contract 'VRFCoordinatorMock' object has no attribute 'callbackWithRandomness'

It's very weird, because the VRFCoordinatorMock file looks ok on my end, and has the callbackWithRandomness function, which is public -I'm therefore at a bit of a loss, and any help would be greatly appreciated!

thanks a lot in advance!

Cheers,

pascal

Here is the code for the test:

def test_can_pick_winner_correctly():
    # Arrange
    if network.show_active not in LOCAL_BLOCKCHAIN_ENVIRONMENTS:
        pytest.skip
    lottery = deploy_lottery()
    account = get_account()
    lottery.startLottery({"from": account})
    lottery.enter({"from": account, "value": lottery.getEntranceFee()})
    lottery.enter({"from": get_account(index=1), "value": lottery.getEntranceFee()})
    lottery.enter({"from": get_account(index=2), "value": lottery.getEntranceFee()})
    fund_with_link(lottery)
    transaction = lottery.endLottery({"from": account})
    request_id = transaction.events["RequestedRandomness"]["requestId"]
    STATIC_RNG = 777
    get_contract("vrf_coordinator").callbackWithRandomness(
        request_id, STATIC_RNG, lottery.address, {"from": account}
    )
    # 777 % 3 = 0
    starting_balance_of_account = account.balance()
    balance_of_lottery = lottery.balance()
    assert lottery.recentWinner() == account
    assert lottery.balance() == 0
    assert account.balance() == starting_balance_of_account + balance_of_lottery

And here is the error trail:

Brownie v1.18.1 - Python development framework for Ethereum

============================================================================================ test session starts ============================================================================================
platform darwin -- Python 3.9.1, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: /Users/pbelouin/Documents/sites/eth/lottery
plugins: eth-brownie-1.18.1, forked-1.4.0, web3-5.27.0, xdist-1.34.0, hypothesis-6.27.3
collected 5 items / 4 deselected / 1 selected                                                                                                                                                               

Launching 'ganache-cli --accounts 10 --hardfork istanbul --gasLimit 12000000 --mnemonic brownie --port 8545'...

tests/test_lottery_unit.py F                                                                                                                                                                          [100%]

================================================================================================= FAILURES ==================================================================================================
______________________________________________________________________________________ test_can_pick_winner_correctly _______________________________________________________________________________________

self = <VRFCoordinatorMock Contract '0xE7eD6747FaC5360f88a2EFC03E00d25789F69291'>, name = 'callbackWithRandomness'

    def __getattribute__(self, name: str) -> Any:
        if super().__getattribute__("_reverted"):
            raise ContractNotFound("This contract no longer exists.")
        try:
>           return super().__getattribute__(name)
E           AttributeError: 'ProjectContract' object has no attribute 'callbackWithRandomness'

../../../../.local/pipx/venvs/eth-brownie/lib/python3.9/site-packages/brownie/network/contract.py:763: AttributeError

During handling of the above exception, another exception occurred:

    def test_can_pick_winner_correctly():
        # Arrange
        if network.show_active not in LOCAL_BLOCKCHAIN_ENVIRONMENTS:
            pytest.skip
        lottery = deploy_lottery()
        account = get_account()
        lottery.startLottery({"from": account})
        lottery.enter({"from": account, "value": lottery.getEntranceFee()})
        lottery.enter({"from": get_account(index=1), "value": lottery.getEntranceFee()})
        lottery.enter({"from": get_account(index=2), "value": lottery.getEntranceFee()})
        fund_with_link(lottery)
        transaction = lottery.endLottery({"from": account})
        request_id = transaction.events["RequestedRandomness"]["requestId"]
        STATIC_RNG = 777
>       get_contract("vrf_coordinator").callbackWithRandomness(
            request_id, STATIC_RNG, lottery.address, {"from": account}
        )
E       AttributeError: Contract 'VRFCoordinatorMock' object has no attribute 'callbackWithRandomness'

tests/test_lottery_unit.py:81: AttributeError
------------------------------------------------------------------------------------------- Captured stdout call --------------------------------------------------------------------------------------------
Deployed!
Deployed lottery!
Funded Contract!
========================================================================================== short test summary info ==========================================================================================
FAILED tests/test_lottery_unit.py::test_can_pick_winner_correctly - AttributeError: Contract 'VRFCoordinatorMock' object has no attribute 'callbackWithRandomness'
====================================================================================== 1 failed, 4 deselected in 3.93s ======================================================================================
Terminating local RPC client...

brownie-config.yaml:

dependencies:
  # - organisation/repo@version
  - smartcontractkit/chainlink-brownie-contracts@1.1.1
  - OpenZeppelin/openzeppelin-contracts@3.4.0
compiler:
  solc:
    remappings:
      - "@chainlink=smartcontractkit/chainlink-brownie-contracts@1.1.1"
      - "@openzeppelin=OpenZeppelin/openzeppelin-contracts@3.4.0"
dotenv: .env
networks:
  default: development
  development:
    keyhash: "0x2ed0feb3e7fd2022120aa84fab1945545a9f2ffc9076fd6156fa96eaff4c1311"
    fee: 100000000000000000
  rinkeby:
    vrf_coordinator: "0xb3dCcb4Cf7a26f6cf6B120Cf5A73875B7BBc655B"
    eth_usd_price_feed: "0x8A753747A1Fa494EC906cE90E9f37563A8AF630e"
    keyhash: "0x2ed0feb3e7fd2022120aa84fab1945545a9f2ffc9076fd6156fa96eaff4c1311"
    link_token: "0x01BE23585060835E02B77ef475b0Cc51aA1e0709"
    fee: 100000000000000000
    verify: True
  mainnet-fork:
    eth_usd_price_feed: "0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419"
wallets:
  from_key: ${PRIVATE_KEY}

And, finally, the code for get_contract():

def get_contract(contract_name):
    """This function will grab the contract addresses from the brownie config
    if defined, otherwise it will deploy a mock version of that contract, and return that
    mock contract.

    Args:
        contract_name (string)

    Returns:
        brownie.network.contract.ProjectContract: the most recently deployed version of this contract.
    """
    contract_type = contract_to_mock[contract_name]
    if network.show_active() in LOCAL_BLOCKCHAIN_ENVIRONMENTS:
        if len(contract_type) <= 0:
            # MockV3Aggregator.lenth
            deploy_mocks()
        contract = contract_type[-1]
        # MockV3Aggregator[-1]
    else:
        contract_address = config["networks"][network.show_active()][contract_name]
        contract = Contract.from_abi(
            contract_type._name, contract_address, contract_type.abi
        )
        # MockV3Aggregator.abi
    return contract

Here is the VRFCoordinatorMock.sol file:

// SPDX-License-Identifier: MIT
pragma solidity 0.6.6;

import "@chainlink/contracts/src/v0.6/interfaces/LinkTokenInterface.sol";
import "@chainlink/contracts/src/v0.6/VRFConsumerBase.sol";

contract VRFCoordinatorMock {
    LinkTokenInterface public LINK;

    event RandomnessRequest(
        address indexed sender,
        bytes32 indexed keyHash,
        uint256 indexed seed
    );

    constructor(address linkAddress) public {
        LINK = LinkTokenInterface(linkAddress);
    }

    function onTokenTransfer(
        address sender,
        uint256 fee,
        bytes memory _data
    ) public onlyLINK {
        (bytes32 keyHash, uint256 seed) = abi.decode(_data, (bytes32, uint256));
        emit RandomnessRequest(sender, keyHash, seed);
    }

    function callBackWithRandomness(
        bytes32 requestId,
        uint256 randomness,
        address consumerContract
    ) public {
        VRFConsumerBase v;
        bytes memory resp = abi.encodeWithSelector(
            v.rawFulfillRandomness.selector,
            requestId,
            randomness
        );
        uint256 b = 206000;
        require(gasleft() >= b, "not enough gas for consumer");
        (bool success, ) = consumerContract.call(resp);
    }

    modifier onlyLINK() {
        require(msg.sender == address(LINK), "Must use LINK token");
        _;
    }
}

[cromewar]

Hello @pbelouin-mpiwg that's a strange error, so we will need more info on this: The complete error log and the code of the test.

Please give it a check to #980 in order to know how to make more complete questions so we could provide you better assistance.

[cromewar]

Ok so the problem seems to be when you call the get_contract("vrf_coodinator") which is strange as function callBackWithRandomness() is part of that contract as you can see here
So you can try separating those transactions:

vrf_coordinator =  get_contract("vrf_coordinator")
vrf_coordinator.callbackWithRandomness(request_id, STATIC_RNG, lottery.address, {"from": account})

Also just in case, delete the build folder and compile again with brownie compile

And be sure the mock is on a folder called test inside the contracts folder.

[pbelouin-mpiwg]

Thank you very much for taking the time to make these suggestions @cromewar , I have tried to separate the transactions, and I've also cleaned up the build folder and recompiled - unfortunately I end up with the same error... Please find below a screenshot of my contracts folder, I think the structure is correct. Very weird isn't it? I'm really at a loss :)

[cromewar]

I'll try to reproduce the error tomorrow and see what happens

[pbelouin-mpiwg]

thanks a lot for all your efforts, I'll keep trying on my end 👍

[pbelouin-mpiwg]

oh but you know I did modify the contract slightly, now that I remember: You see these two lines with the imports, which you can find here: https://github.com/smartcontractkit/chainlink/blob/89c491bd42963c69bbc4894e8226fab92fcda204/contracts/src/v0.6/tests/VRFCoordinatorMock.sol#L4

I did modify the relative paths to absolute paths, and changed

import "../interfaces/LinkTokenInterface.sol";
import "../VRFConsumerBase.sol";

to

import "@chainlink/contracts/src/v0.6/interfaces/LinkTokenInterface.sol";
import "@chainlink/contracts/src/v0.6/VRFConsumerBase.sol";

That might be the reason, I'll change this and see if it helps!

[pbelouin-mpiwg]

I figured it out, it was a typo in the function's name:

callback vs callBack!!!!

Thank you again for your help, I'll keep forging ahead!

[cromewar]

Nice catch, I'm glad is solved now.