TypeError in Hardhat – Fixing TypeError: ethers.getSigners is not a function in Hardhat Tutorial

ethers.jshardhat

I am following this tutorial https://hardhat.org/tutorial/testing-contracts.html and I get this unexpected error:

const { expect } = require("chai");
const { ethers } = require("ethers");

describe("Token contract", function() {
  it("Deployment should assign the total supply of tokens to the owner", async function() {
    const [owner] = await ethers.getSigners();
    const Token = await ethers.getContractFactory("Token");

    const hardhatToken = await Token.deploy();

    const ownerBalance = await hardhatToken.balanceOf(owner.address);
    expect(await hardhatToken.totalSupply()).to.equal(ownerBalance);
  });
});




$ npx hardhat test

TypeError: ethers.getContractFactory is not a function

Best Answer

Two things happened:

require("@nomiclabs/hardhat-waffle"); was missing in hardhat.config.js (as mentionned at the end of https://hardhat.org/tutorial/creating-a-new-hardhat-project.html)
const { ethers } = require("ethers"); should be replaced by const { ethers } = require("hardhat"); or removed as it is available in the global scope.

Related Solutions

Solidity – How to Get the Array Length in Ethers.js and Hardhat

The length of a public array is not exposed by default in solidity.

You can either define a specific solidity function for it :

function getLength() public view returns (uint256) {
   return functionCaller.length;
}

And call that function in your test.

Or directly from ethers.js, read the storage slot of your array (in your example it's in storage slot 0) which holds its length (see the documentation). Be careful though, changing your contract's storage layout may change the storage slot of the array, thus, invalidating your test.

describe("Validate length on push", function () {
  it("Should increment the length after a push is done", async function () {
    const contract = await ethers.getContractFactory("A");
    const instance = await contract.deploy();
    await instance.deployed();

    // Read storage slot 0 holding the length of the array
    const initialLength = ethers.BigNumber.from(await ethers.provider.getStorageAt(instance.address, 0));

    expect(initialLength.eq(0)).to.equal(true);

    await instance.test();

    // Read storage slot 0 holding the length of the array
    const newLength = ethers.BigNumber.from(await ethers.provider.getStorageAt(instance.address, 0));

    expect(newLength.eq(1)).to.equal(true);
  });
});

I hope that answers your question.

Best Answer

Related Solutions

Solidity – How to Get the Array Length in Ethers.js and Hardhat

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