Blockchain CBDE Exam Practice Test Instant Access

Question 1

Why is Unit-Testing so important?

AIt helps you to find bugs, regression bugs and sometimes also helps you to understand your code from different angles.

BIt is a great way to spend time on something that you get paid for. But ultimately it will just slow down the development process.

Answer : A

Question 2

Using truffle-contract over Web3.js:

Ais a must for every developer, because Web3.js changes so often.

Bis a convenient way because Web3.js is currently still in beta and truffle-contract can handle transactions with JavaScript-promises.

Cthey are both completely different things. Truffle-Contract is a framework while Web3.js is a library.

Answer : B

Question 3

Truffle:

Ais a framework that helps developers with Testing, Deployment and Management of Smart Contracts and Distributed Applications.

Bis a library that helps developers to connect to Ethereum nodes, because it abstracts the JSONRPC interface.

Cis a framework for Java, similar to Web3.js for JavaScript. It's a great way to develop distributed Java enterprise applications.

Answer : A

Question 4

It's not possible to use inheritance from multiple sources in Solidity.

ATrue

BFalse

Answer : B

Question 5

Address.Call vs. Address.Delegatecall:

AAddress.call() is used for calling other contracts using the scope of the called contract in terms of storage variables. Address.delegatecall() is used for libraries, which uses the storage variables of the contract who called. Libraries are a great way to re-use already existing code and delegatecall can make sure that no storage is used from the library, instead it looks like the code is directly copied into the calling contract.

BAddress.delegatecall() is used for calling other contracts using the scope of the called contract in terms of storage variables. Address.call() is used for libraries, which uses the storage variables of the contract who called. Libraries are a great way to re-use already existing code and call() can make sure that no storage is used from the library, instead it looks like the code is directly copied into the calling contract.

Answer : A

Question 6

Address.send() and address.transfer() are considered:

Asafe against reentrancy because of the small gas stipend of 2300 gas.

Bdangerous because they send all gas along, it's better to use address.call.value()().

Answer : B

Question 7

Address.call.value():

Asends the gas stipend of 2300 gas and returns a false on error.

Bsends all the gas along and cascades exceptions.

Csends all the gas along and returns a false on error.

Dsends the gas stipend of 2300 gas and cascades exceptions.

Answer : C

Blockchain CBDE BTA Certified Blockchain Developer - Ethereum Exam Practice Test