Blockchain CBDE Exam Practice Test Instant Access

Question 1

Integrating the community into your testing:

Ais great, because they often find bugs which weren't considered before.

Bis not good, because you might give out secrets.

Answer : A

Question 2

Truffle boxes are a great way:

Ato contribute to the box community which is the distributed file system for truffle.

Bto start with a pre-configured environment for most web-development needs.

Cto use tools that makes boxing of Dapps for different platforms very easy.

Answer : B

Question 3

With the truffle config file you can manage:

Athe amount of gas your contract deployment and transactions, against your contract, will need. This way you can essentially lower the gas costs over traditional web3.js dApps.

Bdifferent Networks to deploy your contracts to. This way you can easily deploy to a local blockchain, the main-net or the Ropsten/Rinkeby Test-Net with only one parameter.

Cyou can manage your secret API keys to the Ethereum Network. This way you can get access to several different Ethereum nodes at the same time without the need to switch your keyfiles.

Answer : B

Question 4

It's easy to write clean-room unit-tests with truffle:

Afor Java, JavaScript, and C++

Bfor JavaScript using Web3.js

Cfor Solidity and JavaScript

Dfor any language, as long as it adheres to the open Testing-Interface from Truffle

Answer : C

Question 5

Unit-Testing on a local chain is important, because it helps you:

Ato run tests quickly and especially for free, compared to continuous deployment on the MainNetwork. This way you save a lot of fees, time and costs.

Bto run tests in an environment where logging is activated. On the Main-Net you have no access to transaction logs and this is ultimately the information you need to debug your contracts.

Cto avoid regression bugs with contracts that are updated constantly on the main-net. Once you update a contract on the main-net, the address stays the same, but the code changes and this can have disastrous side-effects.

Answer : A

Question 6

The difference between address.send() and address.transfer() is:

A.send returns a Boolean and .transfer throws an exception on error. Both just forward the gasstipend of 2300 gas and are considered safe against re-entrancy.

B.send throws an exception and .transfer returns a Boolean on error. Both just forward the gasstipend of 2300 gas and considered safe against re-entrancy

C.send returns a Boolean and .transfer throws an exception on error. .send is considered dangerous, because it sends all gas along, while .transfer only sends the gas stipend of 2300 gas along

D.send and .transfer are both considered low-level functions which are dangerous, because they send all gas along. It's better to use address.call.value()() to control the gas-amount.

Answer : A

Question 7

When solidity is compiled then also Metadata is generated:

Athe Metadata contains the ABI Array, which defines the Interface to interact with the Smart Contract. Metadata can also contain the address of the smart contract when it gets deployed.

Bmetadata contains the address, and the size of the smart contract. The ABI Array is generated externally upon deploying the smart contract.

Cthe ABI array and the Metadata are not generated when solidity is compiled to bytecode, its generated by a migration software which deploys the smart contract on the blockchain.

Answer : A

Blockchain BTA Certified Blockchain Developer - Ethereum Exam Practice Test