Solidity low-level call and fallback function failed in hardhat-deploy

Question

I am using examples in soliditylang.org special functions

My simple contracts are extracted from the link

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.2 <0.9.0;

contract TestPayable {
    uint x;
    uint y;

    fallback() external payable {
        x = 1;
        y = msg.value;
    }

    receive() external payable {
        x = 2;
        y = msg.value;
    }
}

contract Caller {
    function callTestPayable3(TestPayable test) public returns (bool) {
        (bool success, ) = address(test).call{value: 2 ether}("");
        require(success, "low-level call failed");
        return true;
    }
}

My deploy script is using hardhat-deploy

const { network } = require("hardhat");

module.exports = async ({ getNamedAccounts, deployments }) => {
  const { deploy, log } = deployments;
  const { deployer } = await getNamedAccounts();
  console.log("deployer : ", deployer);

  for (const contractName of ["TestPayable", "Caller"]) {
    const arguments = [];

    const contract = await deploy(contractName, {
      from: deployer,
      args: arguments,
      log: true,
      waitConfirmations: 1,
    });

    const chainId = network.config.chainId;
    console.log(
      `deployed ${contractName} at ${contract.address}, chainId: ${chainId}`
    );
  }
};

module.exports.tags = ["all"];

My test script is

const { network, deployments, ethers } = require("hardhat");

!["localhost", "hardhat"].includes(network.name)
  ? describe.skip
  : describe("Unit Tests", function () {
      let testPayable, caller, deployer;

      beforeEach(async () => {
        accounts = await ethers.getSigners();
        deployer = accounts[0];
        await deployments.fixture(["all"]);

        testPayable = await ethers.getContract("TestPayable", deployer);
        caller = await ethers.getContract("Caller", deployer);
      });

      it("caller.callTestPayable3", async function () {
        await caller.callTestPayable3(testPayable.address);
      });
    });

My hardhat.config.js is

require("@nomicfoundation/hardhat-toolbox");
require("hardhat-deploy");

module.exports = {
  solidity: "0.8.18",
  namedAccounts: {
    deployer: {
      default: 0,
    },
  },
};

My package.json is

{
  "dependencies": {
    "hardhat": "^2.14.0",
    "hardhat-deploy": "^0.11.28"
  },
  "devDependencies": {
    "@ethersproject/abi": "^5.7.0",
    "@ethersproject/providers": "^5.7.2",
    "@nomicfoundation/hardhat-chai-matchers": "^1.0.6",
    "@nomicfoundation/hardhat-network-helpers": "^1.0.8",
    "@nomicfoundation/hardhat-toolbox": "^2.0.2",
    "@nomiclabs/hardhat-ethers": "npm:hardhat-deploy-ethers",
    "@nomiclabs/hardhat-etherscan": "^3.1.7",
    "@typechain/ethers-v5": "^10.2.0",
    "@typechain/hardhat": "^6.1.5",
    "chai": "^4.3.7",
    "dotenv": "^16.0.3",
    "ethers": "5.7.2",
    "hardhat-gas-reporter": "^1.0.9",
    "solidity-coverage": "^0.8.2",
    "typechain": "^8.1.1"
  }
}

Deployment was fine, but somehow, when I ran "yarn hardhat test", I got error

Error: VM Exception while processing transaction: reverted with reason string 'low-level call failed'
    at Caller.callTestPayable3 (contracts/fallback_call.sol:22)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at runNextTicks (node:internal/process/task_queues:64:3)
    at listOnTimeout (node:internal/timers:533:9)
    at processTimers (node:internal/timers:507:7)
    at HardhatNode._mineBlockWithPendingTxs (C:\Users\...\node_modules\hardhat\src\internal\hardhat-network\provider\node.ts:1840:23)
    at HardhatNode.mineBlock (C:\Users\...\node_modules\hardhat\src\internal\hardhat-network\provider\node.ts:517:16)
    at EthModule._sendTransactionAndReturnHash (C:\...\node_modules\hardhat\src\internal\hardhat-network\provider\modules\eth.ts:1532:18)

This is the most basic example of low-level call from Solidity site, supposedly to work out of box. Why doesn't it work for me?

Answer 1

TestPayable dont have enough Ether to cover the 2 Ether transfer that was indicated in callTestPayable3 .

We could send Ether to the TestPayable contract within the test like this:

const { network, deployments, ethers } = require("hardhat");

!["localhost", "hardhat"].includes(network.name)
  ? describe.skip
  : describe("Unit Tests", function () {
      let testPayable, caller, deployer;

      beforeEach(async () => {
        accounts = await ethers.getSigners();
        deployer = accounts[0];
        await deployments.fixture(["all"]);

        testPayable = await ethers.getContract("TestPayable", deployer);
        caller = await ethers.getContract("Caller", deployer);
      });

      it("caller.callTestPayable3", async function () {
        await deployer.sendTransaction({
          to: testPayable.address,
          value: ethers.utils.parseEther("5"),
        });

        await caller.callTestPayable3(testPayable.address);
      });
    });

Answer 2

I didn't expect to go through so much hassle to run a example from the official solidity site.

Luckily @Saxtheowl provided the direction. It had a couple typo. Here I summarize the final code

In the test js file, give the caller contract 5 eth.

const { network, deployments, ethers } = require("hardhat");

!["localhost", "hardhat"].includes(network.name)
  ? describe.skip
  : describe("Unit Tests", function () {
      let testPayable, caller, deployer;

      beforeEach(async () => {
        accounts = await ethers.getSigners();
        deployer = accounts[0];
        await deployments.fixture(["all"]);

        testPayable = await ethers.getContract("TestPayable", deployer);
        caller = await ethers.getContract("Caller", deployer);
      });

      it("caller.callTestPayable3", async function () {
        await deployer.sendTransaction({
          to: caller.address,
          value: ethers.utils.parseEther("5"),
        });
        const Balance2 = await caller.provider.getBalance(caller.address);
        console.log("Balance2 : ", Balance2.toString());

        await caller.callTestPayable3(testPayable.address);
      });
    });

In the .sol file, I added "receive() external payable {}" so that caller can receive the 5 eth.

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.2 <0.9.0;

contract TestPayable {
    uint x;
    uint y;

    fallback() external payable {
        x = 1;
        y = msg.value;
    }

    receive() external payable {
        x = 2;
        y = msg.value;
    }
}

contract Caller {
    function callTestPayable3(TestPayable test) public returns (bool) {
        (bool success, ) = address(test).call{value: 2 ether}("");
        require(success, "low-level call failed");
        return true;
    }

    receive() external payable {}
}