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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)

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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.

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    This might sound like a silly question but did you go through the Hardhat tutorial? Feb 18 at 20:43
  • As a side note, I am big fan of Hardhat. I created my own template, which contains best practices for linting, testing and coverage. You may find it helpful! Feb 18 at 20:44
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    YES I could review that part of the documentation but the closest thing I understood is the testing part, so towards the question since I do not know if there was another way to make the interactions directly with the contract. @PaulRazvanBerg Feb 18 at 20:45
  • I'm afraid you will have to rephrase your question in such a way that it is more specific. Feb 19 at 10:01
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    @MajdTL Hardhat is arguably a better development environment than Truffle. It offers features such as multi-solc, mainnet forking and support for TypeScript. It's also extensible - there's a host of community-built plugins that enrich what you can do with Hardhat. Feb 22 at 14:19
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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'
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  • This is very nice. Could you please also add how we may estimateGas() for function calls in hardhat? Aug 2 at 19:12

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