Send ETH to Contract Fails in Tests

Question

I'm trying to send ETH to a contract in tests using hardhat await owner.sendTransaction({to: greeter.address, value: "1000000"}), but it reverts with "function selector was not recognized" error.

You can reproduce this with a basic project -

npm init -y
npm i -D hardhat
npx hardhat # use defaults

edit test/sample-test.js and add the following test case -

  it("Should send ETH to the contract", async function () {
    [owner] = await ethers.getSigners();
    const Greeter = await ethers.getContractFactory("Greeter");
    const greeter = await Greeter.deploy("Hello, world!");
    await greeter.deployed();
    await owner.sendTransaction({to: greeter.address, value: "1000000"});
  });

run tests npx hardhat test and the newly added test will fail with Error: Transaction reverted: function selector was not recognized and there's no fallback nor receive function.

Full test log -

Deploying a Greeter with greeting: Hello, world!
Changing greeting from 'Hello, world!' to 'Hola, mundo!'
    ✔ Should return the new greeting once it's changed (626ms)
Deploying a Greeter with greeting: Hello, world!
    1) Should send ETH to the contract
1 passing (745ms)
  1 failing

Greeter
  Should send ETH to the contract:
Error: Transaction reverted: function selector was not recognized and there's no fallback nor receive function

at Greeter.<unrecognized-selector> (contracts/Greeter.sol:6)
at EthModule._estimateGasAction (/Users/tal/dev/solidity/SendEthToContract/node_modules/hardhat/src/internal/hardhat-network/provider/modules/eth.ts:425:7)
at HardhatNetworkProvider.request (/Users/tal/dev/solidity/SendEthToContract/node_modules/hardhat/src/internal/hardhat-network/provider/provider.ts:118:18)
at EthersProviderWrapper.send (/Users/tal/dev/solidity/SendEthToContract/node_modules/@nomiclabs/hardhat-ethers/src/internal/ethers-provider-wrapper.ts:13:20)

Any idea how to send ETH to the contract?

Answer 1

I stumbled into this question while writing a test on a forked hardhat network, where I wanted to send ETH to a 3rd party contract that doesn't have a receive function or a payable fallback function. I needed this because I then wanted to impersonate the contract to call a permissioned method on another contract that only accepts calls from the first contract.

In case anyone is in the same situation, I'll share my solution using the hardhat_setBalance RPC method, through hardhat-network-helpers library. This can set any balance arbitrarily.

import * as helpers from "@nomicfoundation/hardhat-network-helpers";
// ...
await helpers.setBalance(MyContract.address, hre.ethers.utils.parseEther("1"));

Answer 2

Update: As pointed out by @Nergon, there's an answer that explains this phenomena.

To send ETH to a contract without using a payable function, it needs to have a function using special solidity keyword receive to allow receiving ETH without calling a function.

receive() external payable

---

Seems that a contract can receive ETH only through a payable function.

ETH receiving function should look something like this -

function receiveETH() public payable {
    // code
}

it can then receive ETH in tests using -

await farmer.receiveETH({value: ethers.utils.parseEther("1.0")});