# Kotlin Skills Test and Verified Kotlin Score > A Kotlin skills test for Android on coroutines and null safety, plus live Jetpack Compose sessions and connected GitHub repos. Prove your Kotlin skills. Source: https://getlemma.io/skills/kotlin Writing Kotlin that looks like Java with fewer semicolons is common. Lemma shows whether you write idiomatic Kotlin, through live sessions, adaptive assessments and the repositories you connect. How Kotlin is assessed ## What Kotlin competence looks like A strong Kotlin developer uses the language as designed. Null safety is handled with intent rather than double bangs, data and sealed classes model state, and extension functions keep code readable without hiding behaviour. They choose between read-only and mutable collections deliberately. On Android, they run work in coroutines with the right dispatcher and scope, so nothing leaks when a screen closes. They expose state from view models as flows, build UI in Jetpack Compose without needless recomposition, and know how lifecycle changes such as rotation affect what the user sees. ### Null safety Nullable types, safe calls and smart casts used to remove null pointer crashes rather than hide them. ### Coroutines and Flow Scopes, dispatchers, cancellation, and flows for streaming state to the UI. ### Sealed and data classes Modelling UI state and results so every case is handled at compile time. ### Jetpack Compose Composable functions, state hoisting and avoiding unnecessary recomposition. ### Android architecture View models, repositories and dependency injection that survive lifecycle changes. ### Idiomatic Kotlin Extension functions, scope functions and collection operations used for clarity, not cleverness. ## What counts as evidence of Kotlin skills? An app store link does not say who built what. Lemma records Kotlin evidence that does: sessions with another developer, an adaptive test and repositories linked from your own account. Each entry below shows its source. See the [evidence methodology](https://getlemma.io/methodology#evidence-types) for how each source is weighed. [Live session](https://getlemma.io/product/sessions) ### Compose and coroutines session Build a screen or fix a coroutine bug with an Android practitioner. They rate how you manage state, scopes and lifecycle. [Adaptive assessment](https://getlemma.io/product/assessments) ### Adaptive Kotlin assessment Scenarios test null safety, coroutine cancellation and sealed class modelling. Harder rounds show a coroutine that leaks after a screen closes, and you pick the fix. [GitHub connector](https://getlemma.io/product/passport) ### A Kotlin project via GitHub Connect an Android or server-side Kotlin repository, or a specific commit. Lemma checks it exists and that you have access. [AI tutor practice](https://getlemma.io/product/ai-tutor) ### Coroutine practice with the AI tutor Drill scopes, dispatchers and Flow operators with adaptive exercises. Drills add a small, capped amount to practice and help you prepare for proof. ## How is a Kotlin skills test run on Lemma? The Kotlin test adapts as you go, between 15 and 25 questions on device, lifecycle and offline problems, getting harder while you answer correctly. Together with sessions and linked work it sets your Kotlin SCI, where older evidence slowly counts for less. [How the SCI score is calculated](https://getlemma.io/product/sci)[How adaptive skills assessments work](https://getlemma.io/product/assessments)[Practise Kotlin 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. ### Work on a screen live Book a session with a Kotlin practitioner and build or debug part of an Android app. They look at your state model, coroutine scopes and how you handle configuration changes. 2. ### Pass the adaptive assessment The Kotlin assessment moves with your answers, covering null safety, coroutines, Compose and idiomatic patterns. Harder scenarios count for more, and each one is timed. 3. ### Link your repositories Connect Kotlin projects through GitHub so your sessions and assessment sit beside real code. Recent work keeps the skill fresh on your Passport. ## Kotlin skills: common questions ### How do I prove Android development skills to an employer? Combine three things: a live session where an Android practitioner watches you build or debug a Compose screen, an adaptive Kotlin assessment, and a connected GitHub repository. Together they show how you work, which a list of apps alone can't. ### What Kotlin coroutine concepts should I understand? Structured concurrency, scopes tied to lifecycles, dispatchers, cancellation and exception handling, plus Flow for streams of state. These come up in Lemma's Kotlin assessment because most real Android bugs around threading trace back to them. ### Is Kotlin only useful for Android? No. Kotlin also runs on the server and across platforms with Kotlin Multiplatform. Lemma's Kotlin skill covers the language itself, so evidence from server-side work counts too. Android-specific skills are reflected in sessions and in mobile development evidence. ### How do I move from Java to Kotlin and show it? Learn null safety, data and sealed classes, and coroutines first, because that is where Java habits show. Then prove it: take Lemma's Kotlin assessment and book a session where a practitioner reviews code you converted. Connect the repository to back it up. ## Skills related to Kotlin [Browse the skills directory](https://getlemma.io/skills) [### Mobile development Evidence for building mobile apps that work offline, stay fast and survive real devices. Evidence for mobile development](https://getlemma.io/skills/mobile-development)[### Swift Show how you build iOS apps in Swift and SwiftUI, from state to concurrency. Evidence for Swift](https://getlemma.io/skills/swift)[### UI/UX design Show that your interfaces are usable, accessible and consistent, not just attractive. Evidence for UI/UX design](https://getlemma.io/skills/ui-ux-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 Kotlin evidence record. Lemma is in early access. Request an invite and we will email you when your place is ready.