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This tutorial describes how to mint an NFT on the Ethereum blockchain using Ethers via the ethers.js library, and our smart contract from Part I: How to Create an NFT. We'll also explore basic test se
Estimated time to complete this guide: ~10 minutes
Plus, be sure to check out the rest of our NFT tutorial series:
In another tutorial, we learned how to mint an NFT using Web3 and the OpenZeppelin contracts library. In this exercise, we're going to walk you through an alternative implementation using version 4 of the OpenZeppelin library as well as the Ethers.js Ethereum library instead of Web3.
We'll also cover the basics of testing your contract with Hardhat and Waffle. For this tutorial I'm using Yarn, but you can use npm/npx if you prefer.
Lastly, we'll use TypeScript. This is fairly well documented, so we won't cover it here.
In all other respects, this tutorial works the same as the Web3 version, including tools such as Pinata and IPFS.
As a reminder, "minting an NFT" is the act of publishing a unique instance of your ERC721 token on the blockchain. This tutorial assumes that that you've successfully deployed a smart contract to the Ropsten network in Part I of the NFT tutorial series, which includes installing Ethers.
OpenZeppelin is library for secure smart contract development. You simply inherit their implementations of popular standards such as ERC20 or ERC721, and extend the behavior to your needs. We're going to put this file at contracts/MyNFT.sol.
Create the file tasks/nft.ts containing the following:
You'll notice our tasks imported a few helpers. Here they are.
Note that the final getProvider() function uses the ropsten network. This argument is optional and defaults to "homestead" if omitted. We're using Alchemy of course, but there are several supported alternatives.
Under your test directory, create these files. Note that these tests are not comprehensive. They test a small subset of the ERC721 functionality offered by the OpenZeppelin library, and are intended to provide you with the building blocks to create more robust tests.
test/MyNFT.spec.ts (unit tests)
tasks.spec.ts (integration specs)
test-helpers.ts Note this require the NPM libraries imported, including sinon, chai, and sinon-chai. The sinon.restore() call is necessary due to the use of stubbing.
Here's our fairly bare bones hardhat.config.ts.
Note the conditional to only invoke dotenv if we're not running tests. You might not want to run this in production, but rest assured that dotenv will silently ignore it if the .env file isn't present.
Now that we've put these files in place, we can run hardhat to see our tasks (excluding the built-in tasks for brevity).
Forget the arguments to your task? No problem.
To run our tests, we run hardhat test.
In this tutorial, we've created a firm foundation for a well tested NFT infrastructure based on Solidity. The wallet provided by waffle.provider.getWallets() links to a local fake Hardhat Network account that conveniently comes preloaded with an eth balance that we can use to fund our test transactions.