Blockchain Developer Entry Test (3-Hour Challenge)

Welcome to the entry test! You have 3 hours to complete the entire assessment.

Important

You must complete BOTH PART 1 (Skills Marketplace) and PART 2 (Secure Lottery) for all parts of this assessment.

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Timeline & Submission

• Duration: 3 Hours
• Submission: Fork this repo, commit regularly (every 15-30 mins), and push to your fork.

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Prerequisites

Ensure you have:

• Node.js (v20+) & npm
• Git configured (git config user.name "Your Name")
• VS Code (Solidity extension by Juan Blanco recommended)
• A GitLab/GitHub account to host your fork

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Getting Started

1. Fork & Clone

1. Fork this repository to your own namespace.
2. Clone your forked repo:

   git clone [YOUR_FORK_URL]
   cd blockchain_dev_entry_test

2. Environment Setup

# Install dependencies (Hardhat + Toolbox)
npm install --save-dev hardhat @nomicfoundation/hardhat-toolbox

# Initialize Hardhat (if not already initialized)
npx hardhat 
# Choose: Create an empty hardhat.config.js

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Assessment Structure

Part A: MCQ & Theory (PartA_MCQ_Answers.md)

• Answer ALL questions for BOTH PART 1 and PART 2.
• Provide clear reasoning for your choices.

Part B: Design & Implementation

You are provided with two contract skeletons in contracts/:

1. SkillsMarketplace.sol (PART 1)
2. SecureLottery.sol (PART 2)

Your Tasks for BOTH contracts:

1. Implementation: Complete the TODO sections in both .sol files.
2. Design Documentation: Fill in PartB_Design.md detailing your architectural choices, security measures, and trade-offs.
3. Test Planning: Fill in PartB_Tests.md with your test scenarios.
4. Test Implementation: Create a test/ directory and implement automated tests for both contracts using Hardhat.
   • Example: test/SkillsMarketplace.test.js and test/SecureLottery.test.js
   • Run tests with: npx hardhat test

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Functional Specifications

PART 1: Skills Marketplace

• Worker Management: Implementation of registerWorker with input validation and duplicate prevention.
• Gig Workflow: Implementation of postGig (accepting payments), applyForGig, and submitWork.
• Payment & Security: Implementation of approveAndPay using the Checks-Effects-Interactions pattern to prevent reentrancy attacks.
• Events: Proper emission of events for all state-changing operations.

PART 2: Secure Lottery

• Participation: Implementation of enter with minimum entry requirements and multi-entry support.
• Winner Selection: A selectWinner function that calculates a "winner" from total entries and distributes the pot (90% to winner, 10% to owner).
• Randomness Challenge: Application of a secure randomness mechanism (e.g., using block data or VDF concepts).
• Safety: Implementation of an emergency circuit breaker (pause/unpause) and reentrancy protection.

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File Structure

blockchain_dev_entry_test/
├── contracts/
│   ├── SkillsMarketplace.sol     # Complete this (Scenario 1)
│   └── SecureLottery.sol         # Complete this (Scenario 2)
├── test/                         # [NEW] Create your tests here
├── PartA_MCQ_Answers.md          # Complete ALL questions
├── PartB_Design.md               # Document BOTH designs
├── PartB_Tests.md                # Describe BOTH test plans
└── docs/                         # Reference materials

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Tips for Success

• Security Matters: We check for Reentrancy, Access Control, and Integer Handling.
• Gas is Money: Mention gas optimization strategies in your design document.
• Commit History: We look at your commit frequency to understand your workflow.

All the best!