CBSE Blockchain System Testing 2 — Questions and Answers
Question 1: Which testing technique is most effective for discovering re-entrancy vulnerabilities in smart contracts?
- Static code analysis
- Fuzz testing with recursive call injection (Correct answer)
- Load testing
- Unit testing with mocked external calls
Correct answer: Fuzz testing with recursive call injection
Fuzz testing with recursive call injection generates unexpected re-entrant call sequences that static analysis may miss.
Question 2: A blockchain tester wants to verify that a node correctly enforces the longest-chain rule during a network partition. Which test environment best supports this?
- Single-node testnet
- Simulated network with configurable partition controls (Correct answer)
- Mainnet fork snapshot
- Ganache in-memory blockchain
Correct answer: Simulated network with configurable partition controls
A simulated network with configurable partition controls lets testers isolate node clusters and observe fork-resolution behavior.
Question 3: During penetration testing of a blockchain node's RPC interface, which attack vector should be tested first?
- 51% attack simulation
- Unauthenticated JSON-RPC method exposure (Correct answer)
- Eclipse attack
- Sybil node injection
Correct answer: Unauthenticated JSON-RPC method exposure
Unauthenticated JSON-RPC exposure is the most common and immediately exploitable misconfiguration on blockchain nodes.
Question 4: What does a negative gas limit test in Ethereum smart contract testing verify?
- That the contract reverts when gas exceeds the block limit
- That the EVM rejects transactions with an invalid or zero gas limit (Correct answer)
- That miners can set arbitrary gas prices
- That gas estimation tools return accurate values
Correct answer: That the EVM rejects transactions with an invalid or zero gas limit
Testing with zero or invalid gas limits verifies that the EVM correctly rejects malformed transactions before execution.
Question 5: In a blockchain security audit, which property is verified by 'liveness testing'?
- That the network eventually processes valid transactions (Correct answer)
- That node software cannot be remotely crashed
- That private keys are stored securely
- That block hashes are collision-resistant
Correct answer: That the network eventually processes valid transactions
Liveness testing confirms that the blockchain system continues to make progress and process valid transactions under normal and adverse conditions.
Question 6: Which tool is specifically designed for automated security testing of Solidity smart contracts via symbolic execution?
- Truffle
- Hardhat
- Mythril (Correct answer)
- Ganache
Correct answer: Mythril
Mythril uses symbolic execution and taint analysis to automatically detect security vulnerabilities in Solidity contracts.
Question 7: A tester discovers that a DeFi protocol's oracle aggregator accepts a single data source. What vulnerability class does this represent?
- Denial of service
- Single point of failure / oracle manipulation (Correct answer)
- Integer overflow
- Access control bypass
Correct answer: Single point of failure / oracle manipulation
Relying on a single oracle source creates a single point of failure that attackers can manipulate to feed false price data.
CBSE Blockchain System Testing 2
Which testing technique is most effective for discovering re-entrancy vulnerabilities in smart contracts?