Contract Lifecycle: Design, Development, and Deployment BDC Practice Questions (Page 1)

Questions 1–5

1. 1application · medium

   A team has a live ERC-20 token contract and needs to fix a critical bug in the transfer logic. They want to preserve the token balances and the contract address. Which upgrade strategy should they choose?

   • ADeploy a new token contract and migrate balances manually
   • BModify the existing contract's bytecode and redeploy it
   • CUse a proxy contract with a delegatecall-based upgrade pattern
   • DUse a data migration contract to copy balances to a new contract
   Reveal Solution Discussion Select an answer first
2. 2application · medium

   A developer is designing a contract that will be upgraded frequently. Which design pattern is most appropriate?

   • AAvoid using any modifiers to keep the contract flexible.
   • BWrite all logic in a single contract to simplify upgrades.
   • CUse a library for all functions.
   • DUse a proxy pattern with a separate logic contract.
   Reveal Solution Discussion Select an answer first
4. 3expert · hard

   A developer deployed a contract and verified it on Etherscan. Users report that they can see the source code but cannot interact with the contract's functions on Etherscan. What is the most likely reason?

   • AThe contract was verified with a different compiler version than the one used to deploy.
   • BThe contract has not been verified with the ABI.
   • CThe contract address is incorrect.
   • DThe contract's functions are not marked as `public` or `external`.
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5. 4foundation · easy

   What is a common strategy for upgrading a smart contract while preserving its state?

   • AModifying the bytecode of the deployed contract directly on the blockchain.
   • BDeploying a new contract and manually copying the state from the old contract.
   • CUsing the selfdestruct function to destroy the old contract and deploy a new one.
   • DUsing a proxy pattern where the proxy delegates calls to an upgradable implementation contract.
   Reveal Solution Discussion Select an answer first
6. 5foundation · easy

   What is the primary purpose of writing unit tests for a smart contract?

   • ATo deploy the contract to the mainnet automatically.
   • BTo verify that individual functions behave as expected in isolation.
   • CTo create a user interface for interacting with the contract.
   • DTo estimate the gas cost of the contract deployment.
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