Hardhat Testing – How to Interact with the Functions of Smart Contract in Hardhat

hardhatremixsoliditytesting

I am learning to program in Solidity and have followed a basic tutorial on creating a smart contract from a number counter. The tutorial was followed by using Remix and I was very clear about the structure of the code, the deployment and most importantly the interaction with the functions of my contract through this part of REMIX (next image)

In this section I can interact with the reading and writing functions of my contract.

Now I am trying to perform the same exercise using Hardhat, as I want to know better the whole process of developing a smart contract. I have been able to create my project as well as write the code of my contract again and compile the contract using the command npx hardhat compile but I do not understand how to perform the deployment (in the blockchain that comes with hardat) and more importantly see the part where I can test the functions that my contract has.

From what I have read so far, the process in Hardhat would be to create a test within which I define the calls to my functions and display the results using console.log () – this would be correct, some example link would be appreciated.

Best Answer

Basically, you need to deploy the contract to your local hardhat net just as you would to any other. That means currently you have to set up a deploy.js like in the official hardhat tutorial. I'm assuming you followed the official tutorial at least until Chapter 7: Deploying to a live network and e.g. @nomiclabs/hardhat-ethers is already properly installed.

Preparations

❶ Run:

npx hardhat node

❷ Open a new console window at your project directory. Deploy your smart contract by using the previously mentioned deploy.js. You need the --network parameter to specify that you want to deploy to localhost.

npx hardhat run --network localhost scripts/deploy.js

The script will throw back some useful information. Keep an eye on the second address (designated by the contract's name) – you will need it in Step 4.

❸ Connect to the hardhat console at localhost with:

npx hardhat console --network localhost

❹ Get the ethers.js contract factory and attach to it.

Use the proper name in getContractFactory() and paste the address from step 2 in attach()

const Token = await ethers.getContractFactory("Token")
const token = await Token.attach("0x5FbDB2315678afecb367f032d93F642f64180aa3")

Or in one command:

const token = await (await ethers.getContractFactory("Token")).attach("0x5FbDB2315678afecb367f032d93F642f64180aa3")

Interact with contract

You're in a JavaScript environment. E.g. call the transfer method of the hardhat tutorial. For the complete API, see ethers.js API Docs

Two more tips:

Use await to avoid Promise objects.
.toString() helps you to display uint256 numbers (which are too big for JS).

For a more detailed read, refer to the excellent OpenZeppelin tutorial for hardhat.

> await token.transfer("0xdd2fd4581271e230360230f9337d5c0430bf44c0", 42069)
{
  hash: '0xdc0493ce8ed950b4d4558deb65605ba773067804eacfefd7fc64274a8a805dea',
  ...
> (await token.balanceOf("0xdd2fd4581271e230360230f9337d5c0430bf44c0")).toString()
'42069'

Related Solutions

[Ethereum] How contract owner can interact with smart contract

Please don't be confuse on accessing function using web3js. According to your question..

created a modifier inside contract and applied to few functions May be you are using modifier as below (no hard and fast)

pragma solidity 0.4.22;

contract Token{

    address owneraddress;
    modifier onlyowner {
        require(owneraddress == msg.sender);
        _;
    }

    function Token(){
        owneraddress = msg.sender ;
    }

    function start() onlyowner {
      //your logic here  
    }

    function stop() onlyowner {
     //your logic here
    }
}

This restrict to other address except owner . Here owner is assigned as address by which the contract is deployed, Because here constructor is called once when contract is deployed. so you don't need to worry about any other can access this function except owner address.

Now the case is, If you give contract code and contract address to any one then also other account cannot access this function.

Any one can make there own Interface and access these function and again the result will be same. So this conclude that you do not need to restrict through web3js API.

If you want to specify in web3js part that you are the owner and only you want to access those own able function then there is no worth of giving your contract address and code to anyone, They will use there way so you don't have any control on it. If you are making Dapp and other user use your dapp then you can do in web3js layer. And this can be done as :-

web3.DeployedContractRef.start( { from: owneraddress});

web3.DeployedContractRef.stop( { from: owneraddress});

It might help you !

Smart Contract Error – ‘Returned Values Aren’t Valid’ and Out of Gas Issues

I fixed the similar error by deleting .json files from build/contracts folder and then running truffle migrate in the terminal.

However, the error occurred in Visual Studio Code, not Remix IDE. It appeared after running truffle migrate --reset.

I'd like to add to this comment, after you delete .json files from build/contracts folder the problem persisted until I deleted files from the trash🗑 😅 So make sure trash is empty