Contract Lifecycle: Design, Development, and Deployment BDC Practice Questions (Page 8)

Questions 36–40

1. 36application · medium

   A developer is setting up a new Solidity project and wants to use Hardhat for development and testing. Which set of tools is required in the project?

   • ANode.js, npm, and a text editor only.
   • BTruffle, Ganache, and Web3.js.
   • CHardhat, Ethers.js, and a Solidity compiler (solc).
   • DRemix IDE and MetaMask only.
   Reveal Solution Discussion Select an answer first
2. 37application · medium

   A developer is writing unit tests for a Solidity contract using Hardhat and Ethers.js. The contract has a `mint(address to, uint256 amount)` function that should only be callable by the owner. Which test assertion correctly verifies that a non-owner cannot mint?

   • Aassert(await contract.mint(addr1, 100));
   • Bexpect(contract.mint(addr1, 100)).to.be.reverted;
   • Cawait expect(contract.connect(nonOwner).mint(addr1, 100)).to.be.revertedWith('Only owner');
   • Dawait expect(contract.mint(addr1, 100)).to.emit(contract, 'Minted');
   Reveal Solution Discussion Select an answer first
4. 38application · medium

   A developer has written a smart contract and tested it locally with Hardhat. They now need to deploy it to the Sepolia testnet so that a front-end team can integrate with it. Which deployment approach is most appropriate?

   • ACompile the contract and send the bytecode to the Sepolia network via a raw transaction
   • BDeploy to the local Hardhat network and share the local URL with the front-end team
   • CUse Remix to deploy to the JavaScript VM and export the address
   • DUse a Hardhat deployment script configured with a Sepolia RPC URL and a funded account's private key
   Reveal Solution Discussion Select an answer first
5. 39application · medium

   A developer is writing a Solidity contract for a token sale. The contract must allow the owner to pause transfers during emergencies, but the pause logic must be reusable across multiple functions. The developer wants to avoid code duplication and ensure the modifier is applied consistently. Which Solidity construct should be used?

   • AAn internal function called at the start of each transfer function
   • BA custom modifier that checks a paused state variable and reverts if paused
   • CA base contract with a virtual pause function inherited by all transfer functions
   • DA library function that each transfer function imports and invokes
   Reveal Solution Discussion Select an answer first
6. 40expert · hard

   A team is deprecating an old smart contract that holds user funds. They want to allow users to withdraw their funds but prevent any new deposits. What is the best strategy?

   • ASelfdestruct the contract immediately.
   • BChange the contract's owner to a burn address.
   • CIncrease the gas cost of all functions to discourage use.
   • DPause the contract and add a `withdraw` function that remains active.
   Reveal Solution Discussion Select an answer first