I test backend and distributed systems by writing automated regression, API and integration tests, reproducing failures before fixing them, and wiring those checks into CI so regressions are caught before release. I also build the backend services I test, which shapes how I look for failure modes.

API and integration testing. pytest suites against a FastAPI + PostgreSQL service; Jest + Supertest API-layer tests; Testcontainers-backed integration tests for a Spring Boot API; PostgreSQL integration tests for a Rust service, run in CI. Coverage includes authentication and authorization, validation, negative paths, error mapping and status-code contracts.

Regression tests with red/green proof. A regression test should fail without the fix and pass with it, so I check both directions before calling it done.

Browser and mobile automation. Playwright for end-to-end flows, accessibility checks (axe) and link integrity; Maestro for Android smoke flows on physical devices, written with semantic selectors and no fixed sleeps.

Performance. Grafana k6 smoke, spike, stress and soak profiles with explicit thresholds, reported as test conditions rather than capacity claims.

Quality gates in CI/CD. Lint, type checks and automated suites as blocking steps in GitHub Actions; a Jenkins pipeline and Prometheus/Grafana monitoring in a DevSecOps lab.

Failure diagnosis. Reading CI logs and container state in Linux/Docker environments to separate infrastructure failures from real product defects.

Web & mobile quality. Functional, regression, smoke and exploratory testing, with test cases, environments and evidence recorded so results can be reproduced.

• REST APIs in Python (FastAPI), TypeScript (Express, NestJS, Hono), Java (Spring Boot) and Rust
• Distributed-systems behaviour: durable admission, idempotency keys, at-least-once processing, lease-based recovery (FOR UPDATE SKIP LOCKED)
• Authentication and authorization: JWT, role-based access control
• PostgreSQL, SQLite and Redis; Drizzle and Prisma ORMs
• Docker and Docker Compose environments; Prometheus/Grafana observability

Python · pytest · REST API · Docker · GitHub Actions

• Added REST API regression coverage for cloud-storage object keys containing empty path segments, following the behavior fixed in cvat-ai/cvat#11201.
• Covers both root-level and nested empty-path-segment cases and verifies that valid sibling files remain visible.
• Passed CVAT's full CI pipeline on my fork, including all 54 tests in test_cloud_storages.py and the broader REST API job with 2313 passed and 0 failed.
• Verified the regression red/green in GitHub Actions: both new cases pass with the current fix and fail with HTTP 400, a validation error on the listing's content field, when only the #11201 filter is removed.
• Upstream pull request is open and awaiting maintainer review.

Pull request: cvat-ai/cvat#11412

AI Evaluation & Rubric Management API: a REST API for rubric-based human evaluation of AI outputs, with multi-rater scoring and inter-rater agreement.
Python · FastAPI · PostgreSQL · SQLite · pytest · GitHub Actions · Swagger

• 57 pytest tests covering rubrics, scoring, submissions, agreement statistics and the web UI
• Scoring rules enforced and tested: every criterion scored exactly once, within the scale, no duplicate rater evaluations
• Lint and the test suite run in GitHub Actions; live demo with Swagger docs

PulseStream: a co-developed Rust event processing platform built for bounded concurrency, idempotency and crash recovery.
Rust · PostgreSQL · Docker · GitHub Actions

• 63 tests, including 28 PostgreSQL integration tests run as a separate CI job
• Tests idempotent replays (409 on key reuse), 503 rather than 202 on database outage, and lease reclaim after worker crashes
• CI gates on rustfmt, clippy -D warnings, unit tests, integration tests and build

Employee Management System: a Spring Boot + Next.js app with JWT authentication and role-based access control.
Java · Spring Boot · Next.js · PostgreSQL · Docker · JUnit · Mockito · Testcontainers · Vitest

• 65 JUnit tests, with Mockito unit tests and Testcontainers-based integration tests
• CI runs backend tests, frontend lint, frontend tests and the production build

DevSecOps Lab: a Node/TypeScript task API used to practise quality gates in the delivery pipeline.
TypeScript · Express · PostgreSQL · Jest · Supertest · Docker · Prometheus · Grafana · Jenkins

• 22 unit tests enforced in GitHub Actions against a Postgres 16 service, with JUnit report artifacts
• 28 Jest + Supertest integration tests against a real database (run locally)
• /metrics endpoint with a provisioned Grafana dashboard; the README separates what is enforced from what is only planned

Portfolio site: a React/TypeScript portfolio guarded by automated browser checks.
TypeScript · React · Playwright · axe · Lighthouse CI · GitHub Actions

• Playwright E2E, accessibility and link-integrity suites plus Lighthouse CI, all in GitHub Actions

More testing work: Task Manager QA lab (78 Jest + Supertest tests at 74.6% statement coverage in CI, plus k6 load profiles) · Icon Training mobile QA (Maestro, risk-based test design)