Development tools setup (Hardhat, Remix) in Blockchain / Solidity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Hardhat compile command

What is the expected output when you run npx hardhat compile in a new Hardhat project with a valid contracts/ folder containing Solidity files?

A Compilation finished successfully. Artifacts saved to the artifacts/ directory.

B Error: No Solidity files found in the contracts/ directory.

C Warning: No network configured. Compilation skipped.

D SyntaxError: Unexpected token in Hardhat config file.

💡 Hint

Think about what happens when you compile Solidity contracts with Hardhat.

When you run npx hardhat compile with valid Solidity files, Hardhat compiles them and saves the output artifacts. If no errors occur, it confirms successful compilation.

❓ Predict Output

intermediate

Remix IDE Solidity compilation result

In Remix IDE, after writing a valid Solidity contract and clicking the Compile button, what is the expected result shown in the Compile tab?

A Warning: Remix requires a Hardhat node to compile contracts.

B Error: Remix cannot connect to the Ethereum network.

C SyntaxError: Missing semicolon in Solidity code.

D Compilation successful with no errors or warnings.

💡 Hint

Remix compiles Solidity code directly in the browser.

Remix compiles Solidity contracts in-browser and shows success if code is valid. It does not require external nodes to compile.

🧠 Conceptual

advanced

Hardhat network configuration for local testing

Which Hardhat configuration snippet correctly sets up a local network named 'localhost' on port 8545 for testing?

A "networks": { "localhost": { "url": "http://127.0.0.1:8545" } }

B "networks": { "localhost": { "host": "127.0.0.1", "port": 8545 } }

C "networks": { "localhost": { "endpoint": "http://localhost:8545" } }

D "networks": { "localhost": { "address": "127.0.0.1:8545" } }

💡 Hint

Hardhat uses a URL string to specify network endpoints.

Hardhat network configuration requires a URL key with the full HTTP address including port. Other keys like host or port alone are invalid.

🔧 Debug

advanced

Identify the error in Hardhat config file

Given this Hardhat config snippet, what error will occur when running npx hardhat compile?

module.exports = {
  solidity: "0.8.18",
  networks: {
    localhost: {
      url: "http://127.0.0.1:8545",
    }
  },
  // missing comma here
  paths: {
    sources: "./contracts"
  }
};

A TypeError: Cannot read property 'url' of undefined

B SyntaxError: Unexpected token 'paths' - missing comma after networks object

C Error: Solidity version 0.8.18 not supported

D No error, compilation proceeds normally

💡 Hint

Check punctuation between object properties in JavaScript objects.

In JavaScript objects, properties must be separated by commas. Missing a comma causes a SyntaxError.

🚀 Application

expert

Deploying a contract using Hardhat script

Which script correctly deploys a Solidity contract named MyToken using Hardhat and logs the deployed address?

A

async function main() {
  const MyToken = await ethers.getContractFactory("MyToken");
  const token = MyToken.deploy();
  console.log(`Deployed to: ${token.address}`);
}

main().catch(console.error);

B

async function main() {
  const token = await ethers.deployContract("MyToken");
  console.log(`Deployed to: ${token.address}`);
}

main();

C

async function main() {
  const MyToken = await ethers.getContractFactory("MyToken");
  const token = await MyToken.deploy();
  await token.deployed();
  console.log(`Deployed to: ${token.address}`);
}

main().catch(console.error);

D

function main() {
  const MyToken = ethers.getContractFactory("MyToken");
  const token = MyToken.deploy();
  console.log(`Deployed to: ${token.address}`);
}

main();

💡 Hint

Remember to await deployment and the deployed promise before accessing the address.

The correct deployment script awaits the contract factory, deploys the contract, waits for deployment to finish, then logs the address. Missing awaits or async cause errors or undefined addresses.