CBSE Blockchain System Testing 5

Question 1

A tester is evaluating a blockchain bridge contract and wants to confirm that a double-spend via replayed Merkle proofs is impossible. Which test is most appropriate?

Accepted Answer

Submit the same valid Merkle proof twice and verify the second claim is rejected

Answer

Verify that the bridge emits a Deposit event for each transfer

Answer

Check that the bridge contract's Ether balance matches total deposits

Answer

Test that the bridge owner can pause the contract

Question 2

Which of the following best describes a 'griefing attack' test in the context of blockchain smart contracts?

Accepted Answer

An attacker causes a victim's transaction to fail or become expensive without direct financial gain

Answer

An attacker deploys a competing contract with lower fees

Answer

An attacker steals private keys through phishing

Answer

An attacker mines empty blocks to delay transactions

Question 3

During smart contract testing, a developer notices that arithmetic on uint8 values silently wraps at 255 in older Solidity versions. Which mitigation should the test verify is in place?

Accepted Answer

Use of the SafeMath library or Solidity ^0.8.x built-in overflow checks

Answer

Casting all uint8 values to uint256 before display

Answer

Adding a require statement only on subtraction operations

Answer

Using unchecked blocks for all arithmetic

Question 4

What does a 'front-running' susceptibility test in a DEX smart contract attempt to do?

Accepted Answer

Submit a high-gas transaction that copies a pending transaction's parameters before it is mined

Answer

Test that the contract rejects transactions with insufficient slippage tolerance

Answer

Verify that liquidity providers cannot remove funds during a swap

Answer

Check that price impact calculations are accurate for large trades

Question 5

In a blockchain node security test, what does testing for 'eclipse attack' resistance verify?

Accepted Answer

That an attacker cannot monopolize all of a node's peer connections to isolate it from the honest network

Answer

That the node correctly validates proof-of-work difficulty

Answer

That the node rejects blocks with invalid Merkle roots

Answer

That RPC endpoints require authentication

Question 6

A security audit finds that a contract's constructor sets the owner to msg.sender but the contract is deployed via a factory. What test reveals the resulting ownership vulnerability?

Accepted Answer

Deploy the contract via the factory and verify whether the factory contract or the intended user is recorded as owner

Answer

Deploy the contract directly and verify the owner is the deployer

Answer

Call the transferOwnership function as a non-owner

Answer

Test that the constructor can only be called once

Question 7

Which regression test approach is recommended after patching a reentrancy vulnerability in a smart contract?

Accepted Answer

Re-deploy the original unpatched contract to confirm the attack works, then deploy the patched version and confirm the same attack fails

Answer

Only run unit tests on the patched function in isolation

Answer

Check that the contract ABI has not changed after the patch

Answer

Verify that gas consumption decreased after adding the reentrancy guard