how to hardhat test against a mainnet fork?

Question

I'm using hardhat to fork the polygon mainnet by - npx hardhat node --fork <ALCHEMY RPC ENDPOINT>

now i want to test on this local network. what is the command? npx hardhat test is not working.

Answer 1

You can configure hardhat forking in the hardhat.config file

 networks: {
        hardhat: {
          forking: {
            // eslint-disable-next-line
            enabled: true,
            url: `https://eth-mainnet.alchemyapi.io/v2/${process.env.ALCHEMY_API_KEY}`,
      }

Answer 2

You need to set your mainnet fork in hardhat.config.js

module.exports = {
  solidity: "0.8.9",
  networks: {
    fork: {
      url: "<ALCHEMY RPC ENDPOINT>",
    },
  }
}

And you can just type npx hardhat test --network fork to run the test in your mainnet fork.

Answer 3

Set the hardhat.config.js in the following way

module.exports = {
  solidity: "0.8.9",
  networks: {
    fork: {
      url: "<ALCHEMY RPC ENDPOINT>",
    },
  }
}

Now in one terminal, run the command npx hardhat node

In other terminal, run the command npx hardhat test ./{Your_file_location} --network localhost

After this in the terminal where you had run npx hardhat node, you'll see the calls made over the network like - contract deployment, function calls, gas estimations, etc.

I have attached the picture for your reference. This confirms that your mainnet fork worked!!