Contract verification on Etherscan in Blockchain / Solidity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Solidity contract verification status check?

Given the following Solidity code snippet that queries Etherscan API for contract verification status, what will be the output if the contract is verified?

Blockchain / Solidity

pragma solidity ^0.8.0;

// This is a pseudo-code example to illustrate the concept
// Assume getVerificationStatus() calls Etherscan API and returns a string
contract VerifyStatusChecker {
    function getVerificationStatus() public pure returns (string memory) {
        // Simulated response
        return "Verified";
    }
}

A Compilation Error

B "Pending"

C "Not Verified"

D "Verified"

💡 Hint

Think about what the function returns as a simulated response.

The function getVerificationStatus() returns the string "Verified" as a simulated response, so the output is exactly that string.

🧠 Conceptual

intermediate

Which step is NOT required for contract verification on Etherscan?

When verifying a smart contract on Etherscan, which of the following steps is NOT required?

A Submitting the contract's ABI manually

B Providing the compiler version used

C Uploading the contract source code

D Selecting the correct optimization settings

💡 Hint

Think about what Etherscan generates automatically after verification.

Etherscan automatically generates the ABI after verifying the source code, so submitting the ABI manually is not required.

🔧 Debug

advanced

Why does this contract verification fail on Etherscan?

A developer tries to verify their contract but Etherscan returns a verification failed error. The contract uses Solidity 0.8.12 with optimization enabled. The developer submits the source code but forgets to select optimization in the verification form. What is the likely cause of failure?

A Mismatch in optimization settings between compiled contract and verification form

B Incorrect Solidity version selected

C Source code has syntax errors

D Contract address is incorrect

💡 Hint

Think about what happens if optimization settings differ between compilation and verification.

If optimization was enabled during compilation but not selected during verification, the bytecode hashes won't match, causing verification to fail.

📝 Syntax

advanced

Which Solidity pragma version is compatible with Etherscan verification for a contract compiled with 0.8.12?

You want to verify a contract compiled with Solidity 0.8.12 on Etherscan. Which pragma directive is correct to ensure compatibility?

A pragma solidity 0.8.11;

B pragma solidity ^0.8.12;

C pragma solidity >=0.8.0 <0.9.0;

D pragma solidity ^0.7.0;

💡 Hint

Consider the range of versions allowed by the pragma and the exact compiler version used.

The pragma '>=0.8.0 <0.9.0' includes 0.8.12, ensuring compatibility. '^0.8.12' requires at least 0.8.12 but may exclude some patch versions. '0.8.11' is too low and '^0.7.0' is incompatible.

🚀 Application

expert

How many constructor arguments must be ABI-encoded and submitted during Etherscan verification for this contract?

Consider this Solidity contract: contract Token { string public name; uint256 public supply; constructor(string memory _name, uint256 _supply) { name = _name; supply = _supply; } } When verifying this contract on Etherscan, how many constructor arguments must be ABI-encoded and submitted?

A 1

B 2

C 0

D 3

💡 Hint

Count the parameters in the constructor function.

The constructor has two parameters: a string and a uint256, so two arguments must be ABI-encoded and submitted for verification.