# Blockchain Developer Skills Test and Verified Score > A blockchain developer skills test on smart contract security, plus live contract reviews and connected GitHub repos. See what proves blockchain skills. Source: https://getlemma.io/skills/blockchain In smart contract work, a single unchecked assumption can be expensive and hard to undo on chain. Lemma records how you reason about state, security and gas in live sessions, so your blockchain skill is judged on that reasoning. How blockchain development is assessed ## What blockchain development competence looks like A competent blockchain developer treats every contract as hostile territory. They know the common vulnerability classes, such as reentrancy, unchecked external calls and access control mistakes, and they design to avoid them rather than patch later. They write tests that try to break the contract, not just confirm the happy path. They also understand the platform underneath. They can explain how transactions are ordered and confirmed, why storage writes cost more than reads, and what upgradeability patterns trade away. They choose when logic belongs on chain at all, and they document assumptions so an auditor can check them. ### Smart contract design Structuring contracts, events and storage so behaviour is predictable, auditable and hard to misuse. ### Contract security Reentrancy, access control, oracle manipulation and other vulnerability classes, plus how to prevent them. ### Testing and fuzzing Unit tests, fork tests and property-based fuzzing that actively try to break contract invariants. ### Gas and storage costs Understanding what operations cost and designing data layouts that keep transactions affordable. ### Consensus and transactions How blocks are produced, how transactions are ordered and what finality means for your design. ### Upgrade patterns Proxy patterns, their storage risks and when a non-upgradeable deployment is the safer choice. ## What counts as evidence of blockchain development skills? A line on a CV saying blockchain development is a claim. A reviewed session, an assessed level or a repository linked from your account is evidence. These are the kinds Lemma records against your blockchain development skill, each with where it came from. See the [evidence methodology](https://getlemma.io/methodology#evidence-types) for how each source is weighed. [Live session](https://getlemma.io/product/sessions) ### Reviewing a contract for vulnerabilities A practitioner shares a contract with a flaw in it. In a live session you find the issue, explain how it could be exploited and propose a fix, and they rate your review. [GitHub connector](https://getlemma.io/product/passport) ### Contracts and tests on GitHub Connect a repository containing contracts and their test suite. Lemma checks the repository exists and that your account has access, and re-checks it over time. [Adaptive assessment](https://getlemma.io/product/assessments) ### Scenario questions on chain behaviour Adaptive questions describe realistic situations, such as a failed transfer or a front-run transaction, and ask for the correct diagnosis. Difficulty adjusts with each answer you give. [Live session](https://getlemma.io/product/sessions) ### Teaching a security concept Explaining a vulnerability class to another developer, with a worked example, shows real understanding. Teaching sessions count for more than learning ones in your record. ## How is a blockchain development skills test run on Lemma? The blockchain development test runs 15 to 25 questions and adjusts difficulty to your answers, with scenarios from services under real load. The result counts alongside sessions and linked repositories toward your blockchain development SCI, which favours recent evidence over old. [How the SCI score is calculated](https://getlemma.io/product/sci)[How adaptive skills assessments work](https://getlemma.io/product/assessments)[Practise blockchain development in live skill swap sessions](https://getlemma.io/product/sessions)[Which evidence types count](https://getlemma.io/methodology#evidence-types)[What your Skills Passport shows](https://getlemma.io/product/passport) 1. ### Practise attack patterns The AI tutor sets exercises on common contract vulnerabilities and asks you to explain fixes in your own words. It adapts to your answers. Drills add only a small, capped amount to your practice score. 2. ### Review contracts with a peer Live one-to-one sessions let a practitioner watch you read, test and reason about contract code. Their rating, and the completed session itself, become evidence for this skill. 3. ### Take the adaptive assessment Scenario-based questions on contract security, transactions and gas adjust in difficulty as you answer. Time limits, no back-navigation and non-repeating questions keep the result a fair measure. ## Blockchain development skills: common questions ### How do I prove smart contract skills to a crypto team? Teams want to see how you think about security. Review contracts for vulnerabilities in live sessions with practitioners, connect a repository with contracts and a serious test suite, and pass the adaptive assessment. Your Passport then shows reviewed reasoning, not only deployed code. ### What should a blockchain developer portfolio include? Contracts with clear access control and events, a test suite that includes failure cases and fuzzing, and notes explaining design choices and known risks. Connect that repository to Lemma, then discuss the design in a session so a practitioner can challenge it and record their rating. ### Does Lemma assess a specific chain or language? The skill covers blockchain development as a whole: contract design, security, testing, transactions and gas. Questions use realistic scenarios rather than trivia about one network. In live sessions you work in whatever stack you and the practitioner agree on, and the review focuses on reasoning that transfers. ### Is an audit report better evidence than a Lemma record? An audit you contributed to is strong evidence, and you can keep pointing people to it. Lemma adds a different angle: how you reason in real time, rated by practitioners, plus an adaptive assessment. Together they show both your past work and your current ability. ## Skills related to blockchain development [Browse the skills directory](https://getlemma.io/skills) [### Cybersecurity Evidence of how you find, prioritise and fix real security risks in systems and code. Evidence for cybersecurity](https://getlemma.io/skills/cybersecurity)[### Rust Show that you work with the borrow checker rather than around it, through live code and connected crates. Evidence for Rust](https://getlemma.io/skills/rust)[### System design Show how you reason about scale, failure and trade-offs, in live design sessions reviewed by practitioners. Evidence for system design](https://getlemma.io/skills/system-design) ![Painting of an olive grove in soft sunlight with hills beyond](https://cdn.sanity.io/images/islu4peo/production/613eb3f93566423c9adf45246f2cf1a61437c04c-1680x1120.jpg?w=1080&fm=webp&q=68&fit=max) ## Start your blockchain development evidence record. Lemma is in early access. Request an invite and we will email you when your place is ready.