Things I built.

An open-source library that turns one schema into explained adversarial test inputs - boundary values, i18n, and injection, each with a plain-language reason it might break.

QADoes it label correctly whether a generated value satisfies the field's own constraints (validity: valid / invalid / unknown) - i18n and injection are left "unknown" honestly, because whether they're accepted is exactly the behaviour under test

• TypeScript
• Zod
• OpenAPI
• Open Source
• QA

A menu bar app for cleaning your Mac - lock the keyboard to wipe it, fill the screen with a flat color to reveal smudges, dust, and dead pixels, plus spill first-aid (bonus). No permissions, no data collection; sandboxed and shipped on the Mac App Store.

QAKey-swallow completeness - no keystroke leaks to the app behind the overlay while active (including the accessory-focus regression, verified by hand)

• Swift 6
• AppKit / SwiftUI
• macOS Menu Bar
• Mac App Store
• Zero-permission / Sandboxed

RICE · ICE · MoSCoW · Value × Effort in one workspace - open-source prioritization.

QAOne board component switches the input columns, legend, and formula correctly for each of the four frameworks (RICE / ICE / MoSCoW / Value × Effort)

• Next.js 15
• FastAPI
• PostgreSQL
• Open Source

A timing-sense game where you stop exactly at 11.900 seconds - an MVP for an SKKU EMBA event.

QAMeasurement accuracy is trust - the client clock isn't taken at face value; the server re-validates against its own baseline

• React
• FastAPI
• Render

Daily-refresh service that has AI break down today's trends into four categories.

QADaily auto-generation - guard the regression so one failure can't spread across several days (invisible piled-up regression)

• Next.js
• AI
• Vercel KV

A QA learning platform for picking up testing methodology and automation hands-on - you write tests against practice apps that look like the real thing.

QAdata-testid selectors survive CSS and component-structure changes so E2E holds up on refactors (proving out the learning standard)

• QA
• Education
• React
• FastAPI

Python CLI that finds duplicate Jira issues by embedding their title and description and flagging pairs above a threshold - Excel reports plus usage and cost stats.

QAThe similarity threshold's precision/recall - lowering it yields false positives (unrelated pairs), raising it misses real duplicates; where is the tradeoff set?

• Python
• CLI
• OpenAI
• Jira

Triggers Playwright automation from Jira issues and writes results back as comments.

QAJira round-trip integrity - issue → run → comment reply → status transition runs end-to-end with nothing dropped in between

• Playwright
• Python
• Jira API

A personal parking app that logs your spot by floor and zone and shows it on a home widget (iOS and Android) without opening the app - offline-first, local storage.

QAWhere the widget and app split the same location data (iOS App Group) is the most regression-prone spot - the top priority is "does the location saved in the app always show correctly in the widget?"

• React Native / Expo
• TypeScript
• Home Widget (iOS/Android)
• Offline-first

A food decision advisor that narrows "what should I eat today?" down to 1-3 picks using taste, your current state, and location.

QAAllergens, hard excludes, and constraints are filtered up front by a hard filter (DB query), not a probabilistic LLM, and can never be bypassed (the one place a wrong answer hurts someone)

• React Native
• FastAPI
• AI
• PostgreSQL

A reading roadmap that shows what order to read in for a topic - the goal is showing the path, not a list of recommendations.

QAAnonymous localStorage progress and logged-in server progress don't diverge - and the unsupported import is stated honestly on screen

• React
• TypeScript
• Hono
• Reading

An analysis engine that turns Korean real-estate documents into risk signals.

QASame document, always the same score - with now pinned to FIXED_NOW, does the result exactly match the stored golden?

• Python
• FastAPI
• PDF
• Real Estate

A vocabulary app that builds a daily word habit with spaced review and streaks - a web/mobile/desktop MVP with AI word generation, sentence coaching, and pronunciation scoring.

QADoes review surface at the right moment - D-1 success promotes to D-3, a failed review re-queues to the next day with no next stage, overdue reviews surface oldest-first (pinned by unit tests)

• TypeScript
• PWA
• Capacitor
• OpenAI
• Language Learning

An AI evaluation SaaS that turns release-or-hold decisions into data - just before launch.

QAScore reproducibility - the same inputs (coverage, open defects, change-risk) yield the same confidence score (deterministic rubric)

• SaaS
• AI
• FastAPI
• React

A language-learning app built around the double-translation loop - translate the source into the foreign language, then days later back-translate your own version to your mother tongue and compare what's lost.

QAThe access/refresh flow - on a 401 the one-shot auto-refresh runs exactly once without looping, and falls back to /login safely on failure

• FastAPI
• React
• OpenAI
• Language Learning

A degree-requirement calculator that moves the SKKU EMBA graduation worksheet to the web - enter your courses and it computes requirement fulfillment and the attainable degree.

QASame input, same result - the requirement calc is a side-effect-free pure function with constants, pinned by unit tests on the tricky boundary combos (exactly 45 credits, business 6 / non-business 12, Advanced 18, etc.)

• React 19
• TypeScript
• Supabase
• EMBA

An async, hands-on learning platform for picking up LLM usage with cohort peers - guides, a roadmap, courses, plus a browser-side IDE that runs prompts against the LLM directly.

QAEvery added content card gets the three principles (AI drafts, humans verify, no sensitive data) enforced by the screen structure (removing a human-hands regression)

• FastAPI
• React
• LLM
• Education

A community app for SKKU EMBA members - the member directory, business-card QR sharing, mentoring, schedule, board, and cafeteria menu in one place.

QAThe boundaries of inherited code (token expiry/re-login, network failures, empty states, missed push) hold up in real members' hands, not just a demo

• Flutter
• Firebase
• iOS
• Android

Operations system for a grad-school golf club - from live scoring to payments.

QALive scoring - when several people enter scores at once mid-round, the tally doesn't drift (concurrency)

• Next.js
• Express
• Prisma

A cohort-ops web app for grad-school peers - school-domain OAuth keeps it to the cohort only, with survey, announcements, anonymous feedback, emergency contacts, and meeting rooms in one place.

QAThe @g.skku.edu-restricted OAuth actually blocks non-cohort accounts - no path routes around it

• Next.js 15
• Supabase
• Cloudflare Workers

Access-code archive for sharing course materials with grad-school peers.

QAThe access-code session actually blocks material access for anyone without the code (code-exposure and reuse boundary)

• Vite
• Supabase

An iPadOS-only AI error-notebook - an AI grades your Apple Pencil handwriting step by step, analyzes weaknesses, generates similar problems, and schedules spaced-repetition (FSRS) review. A thin SwiftUI client on a thick FastAPI backend.

QAGrading output always conforms to the structured schema (per-step verdict, error type, evidence) - evidence-free verdicts are caught at the parsing layer

• SwiftUI (iPadOS)
• PencilKit
• FastAPI / Python
• Multimodal LLM
• FSRS (SRS)

Turns a one-paragraph idea into a Project Brief, MVP scope, dev issues, and next steps - exported as a single Markdown doc.

QAGeneration of the four sections (Brief, MVP scope, issues, next steps) doesn't break on empty, vague, or very long one-paragraph input

• Next.js
• TypeScript
• Claude Code

Pairs lecture slides with a recording to draft per-slide study notes - Whisper STT + Claude.

QAWhen aligning the STT transcript to slide boundaries, an offset drift doesn't attach notes to the wrong slide

• React
• FastAPI
• Whisper
• Claude

A 7-day weather forecast on Cloudflare Workers backed by Open-Meteo - search by city (KO/EN) or use your location, no API key needed.

QACity search handles both KO/EN spellings, typos, and non-existent place names safely

• Cloudflare Workers
• TypeScript

Android app that measures a gyroball's RPM in real time from camera and audio frequency.

QAIs it reproducible under the same conditions - a consistent error pattern matters before accuracy (the precondition for correction)

• React Native
• Kotlin
• Monorepo

An all-in-one QA community platform for the QA ecosystem - paused after pivoting to a public-good activity.

QAWith several features (posts, resources, profiles) bundled into one platform, the access-permission boundaries don't leak between beginners, practitioners, and leads

• QA
• Community
• Platform

A full-stack tool where you paste a document URL (a public Notion page) and GPT-4o-mini drafts and groups a QA test checklist - an experiment testing "from design/docs to QA" (shift-left), wired up through auth and payments.

QAHow do you measure an auto-generated checklist's accuracy and omissions and prevent regressions - without that, plausible items still don't earn trust (the core problem this project didn't solve)

• QA
• OpenAI
• FastAPI
• React
• SaaS