Blockchain Development Frameworks (Truffle, Hardhat) BDC Practice Questions (Page 8)

Questions 36–40

1. 36application · medium

   A team is using Hardhat to test a Solidity contract that has a function which should revert when called with a zero address. They want to verify that the revert reason is correctly emitted. Which testing approach is most appropriate?

   • AWrite a test using chai's expect and the .to.be.revertedWith('Zero address') matcher from Hardhat Chai Matchers.
   • BDeploy the contract to a public testnet and manually call the function from a wallet to observe the revert.
   • CWrite a script that catches the error and logs it, then manually inspect the log to confirm the revert reason.
   • DUse Truffle's develop console and invoke the function to see the error message in the console output.
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2. 37application · medium

   A developer is using Hardhat and has written a Solidity contract that imports another local contract. When they run `npx hardhat compile`, the compiler cannot find the imported file. What is the most likely cause?

   • AThe import statement uses a relative path that starts with `./` instead of `../`.
   • BThe imported file is not in the `contracts/` directory or its subdirectories.
   • CThe compiler version in `hardhat.config.js` does not match the pragma in the contract.
   • DThe contract has not been added to the `sources` array in `hardhat.config.js`.
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4. 38expert · hard

   A developer is troubleshooting a failing test in Hardhat. The test calls a contract function that is expected to emit an event, but the test fails because the event is not found. The contract code looks correct. What is the most likely cause and solution?

   • AThe contract was not recompiled after changes; run npx hardhat compile to update the artifacts.
   • BThe event name is misspelled in the test; check the contract ABI for the exact event name.
   • CThe test is using the wrong contract instance; ensure the deployed contract address is correct.
   • DThe transaction was mined but the event was not emitted because the function reverted; use expect(...).to.be.reverted to confirm.
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5. 39application · medium

   A developer is writing tests for a Solidity contract that has a function that should revert when called with a zero address. The project uses Hardhat with the toolbox plugin. Which test assertion should they use to verify the revert behavior?

   • Atry { await contract.functionCall(zeroAddress); } catch (e) { assert.equal(e.message, 'Invalid address'); }
   • Bassert.throws(contract.functionCall(zeroAddress), 'Invalid address');
   • Cawait contract.functionCall(zeroAddress).should.throw('Invalid address');
   • Dawait expect(contract.functionCall(zeroAddress)).to.be.revertedWith('Invalid address');
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6. 40application · medium

   A developer is setting up a Hardhat project to deploy a contract to a public testnet. The team wants to avoid committing the private key to the repository. The developer has already installed the @nomicfoundation/hardhat-toolbox plugin. What is the recommended way to configure the network and supply the private key?

   • AUse the Truffle-style migrations folder and place the private key in a separate JSON file that is not committed.
   • BStore the private key in the hardhat.config.js as a constant and encrypt the file with a password before pushing.
   • CSet the private key in a .env file, load it with dotenv, and reference process.env.PRIVATE_KEY in the networks section of hardhat.config.js.
   • DHardcode the private key in hardhat.config.js and rely on .gitignore to exclude the file from the repository.
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