mint-nft.ts

import {ethers} from 'ethers';

const contractArtifact = require("../artifacts/contracts/MyNFT.sol/MyNFT.json");

export async function mintNft(
    tokenURI: string,
    env: NodeJS.ProcessEnv,
    provider: ethers.providers.Provider,
    contractAddress: string,
) {
    const publicKey = env.PUBLIC_KEY!;
    const privateKey = env.PRIVATE_KEY!;
    const wallet = new ethers.Wallet(privateKey, provider);
    await wallet.getBalance().then((gp) => console.log('gp', gp))

    const nftContract = new ethers.Contract(contractAddress, contractArtifact.abi, wallet);

    await nftContract.mintNFT(publicKey, tokenURI, { gasLimit: 500_000})
        .then((result: any) => console.log(`result`, result))
}

MyNFT.spec.ts

import { mintNft } from "../lib/mint-nft"
import {ethers, waffle} from "hardhat";
import { Contract } from "@ethersproject/contracts"

describe("MyNFT", function () {
  let signerAddress: string;
  const tokenURI = "http://example.com";
  let env: NodeJS.ProcessEnv;
  let deployedContract: Contract;

  beforeEach(async () => {
    const MyNft = await ethers.getContractFactory("MyNFT");
    const hardhatMyNft = await MyNft.deploy();
    const [wallet] = waffle.provider.getWallets()
    const connected = hardhatMyNft.connect(wallet)
    deployedContract = await hardhatMyNft.deployed();

    env = {
      PUBLIC_KEY: wallet.address,
      PRIVATE_KEY: wallet.privateKey
    }
  })

  it("works", async function () {
    mintNft(tokenURI, env, ethers.provider, deployedContract.address);
  });
});

script.ts

const provider = ethers.getDefaultProvider("ropsten", {
  alchemy: '8-bL_8THTfHufs-0RcDbsDLyOoM1epiC', // This is fake; use yours, at the end of your Alchemy API URI.
});

// These are fake values for example. Set them in your actual environment.
process.env = {
  PUBLIC_KEY: "0xFBDE00762b7157e766560547F749351659483A64",
  PRIVATE_KEY: "0x2c204284da092c30b0b24c13b08ed8e096a09571f6030ccc81a5f93246be17c9",
}

const deployedContractAddress = "0x81c587EB0fE773404c66b5f5542c1d267C470eED";
mintNft("http://example.com/your-endpoint", process.env, provider, deployedContractAddress);