yosuancrespo
Senior Qa Engineer
Results-driven Senior QA Engineer and QA Lead with 17+ years of experience in software quality, leveraging AI-augmented manual and automation testing to build scalable frameworks and CI/CD pipelines. I specialize in delivering high-quality releases for complex Web, Mobile, API and Blockchain systems.
Core Expertise:
• AI & Innovation: Utilizing Large Language Models (LLMs), AI tools and AI Agents (Claude, ChatGPT, Cursor, GitHub Copilot, Antigravity, n8n) to accelerate script generation, optimize test design, increase test coverage and reduce critical defects.
• Automation Architecture: Architecting full-stack solutions using Playwright, Cypress, Selenium, Pytest and Appium for E2E, integration and regression testing that support collaborative development and robust CI/CD execution.
• Web3, DeFi & Blockchain: Validating smart contracts and DApps on Ethereum, Solana, Cardano, Polygon, BSC, among other blockchains, ensuring secure transactions.
• Leadership: Bilingual (English-Spanish) leader skilled in mentoring teams, driving Shift-Left testing, TDD and BDD adoption in Agile environments (Scrum, Kanban), aligning quality initiatives with business objectives.
Tech Stack:
• Languages: TypeScript, JavaScript, Python, Java, Solidity, Rust, Go, Bash, SQL (PostgreSQL, MySQL), NoSQL.
• Automation, API & Test Mgmt: Playwright, Cypress, Selenium, Pytest, Cucumber, Appium (iOS/Android), Postman, GraphQL, REST, REST Assured, Supertest, Swagger, Jira, Confluence, Xray, TestRail.
• Cloud & DevOps: AWS, Azure, GCP, Oracle Cloud, Docker, Kubernetes, Terraform, Linux, Github Actions, Jenkins, GitLab CI, Datadog, Elasticsearch.
• Performance & AI: JMeter, k6, Large Language Models (LLMs), Claude, ChatGPT, Cursor, GitHub Copilot, Antigravity, n8n, AI Agents.
GitHub Portfolio: github.com/yosuancrespo
Experience: 11 years
Yearly salary: $96,000
Hourly rate: $50
Nationality: 🇪🇸 Spain
Residency: 🇪🇸 Spain
Experience
Senior QA Automation Engineer
Serokell 2025 - 2025
Client: Midnight Network (Cardano ecosystem) • Built the QA layer for Midnight Toolkit and smart-contract testing, focusing on TypeScript + Vitest v3 E2E/integ tests, GraphQL Indexer API queries/subscriptions and Dockerized local env, utilizing AI and LLMs for intelligent edge-case generation. Authored 50+ E2E/integ cases covering ~99% of critical paths and cut local env setup from ~45 min to ~15 min (−67%). • Designed and automated smart-contract testing with Midnight Toolkit: reproducible local deployments, on-chain state-transition & event assertions and negative-path coverage; added 15+ state/event assertions and 18+ negative cases, preventing 4 critical regressions pre-merge; integrated with Vitest + Docker + Indexer GraphQL for end-to-end validation. • Authored and maintained Rust integration tests, validating tagged (de)serialization and well-formedness checks; implemented 20+ integration tests and reduced flaky failures by ~60% across the suite. • Built TS helpers for transaction generation & viewing keys; exercised Indexer GraphQL mutations/subscriptions to verify shielded and unshielded txs visibility and event streams; published 10+ reusable helpers, reducing boilerplate by ~40% and cutting teammate onboarding from ~1 day to ~2 hours (−80%). • Standardized CI workflows and added negative-test coverage to reduce flakiness and tighten failure signals; migrated key tests, halved test runtime (≈35 → 18 min) and improved per-PR feedback speed ~2×. • Key Technologies & Tools: TypeScript, Rust, Cardano, Vitest, GraphQL, Postman, Claude, Cursor, ChatGPT, Large Language Models (LLMs), Prompt Engineering, Docker, GitHub, GitHub Actions, Jira, Xray, Cucumber, Confluence, Notion, Slack, Icepanel.
Regional Manager and Business Developer
Rentible 2022 - 2023
• Pioneered Web3 adoption in real estate by spearheading regional management and business development for Rentible, a cutting-edge platform facilitating crypto-based property rentals via smart contracts. • Represented Rentible at The Capital 2022 Metaverse Conference (CoinMarketCap), generating 10+ high-value leads and expanding brand visibility in the crypto ecosystem. • Secured strategic partnerships with 12 real-estate agencies and proptech startups, boosting platform listings by 150% and driving a 4x increase in monthly rental volume using Salesforce. • Onboarded 40+ new clients, property owners and asset managers, by guiding them through smart-contract setup, KYC/compliance and platform integration. • Conducted 25+ stakeholder interviews and needs-analysis sessions to refine user journeys, resulting in a 25% uptick in user engagement metrics. • Audited and optimized website UX/UI, collaborating with designers and developers to improve load times by 40% and streamline the rental workflow. • Authored comprehensive user guides, FAQs and video tutorials that reduced onboarding support tickets by 65%. • Led investor outreach and due-diligence efforts, closing a pre-seed round and establishing ongoing VC relationships. • Orchestrated PR campaigns across crypto and real-estate media channels, securing press and amplifying social media community growth by 300%.
QA Lead
Freeway 2022 - 2023
• Led the team, defining and executing a comprehensive test strategy (Manual & Automated) while simultaneously overseeing project execution within an Agile framework, for the integration with the Bitcoin network and DeFi applications. • Implemented full-stack automation integrated into Azure and mentored QA Engineers, reducing critical bugs in production by 35% and accelerating release cycles by 25%. • Executed a wide range of testing types: Unit, API, Automation (Cypress, Selenium, Playwright, Postman), E2E, Regression, Smoke, Integration, Exploratory, UAT and Cross-Functional (performance with Gatling and JMeter, Security, Compatibility, Usability, Accessibility, Scalability). • Specialized in testing blockchain transactions for decentralized finance products across networks including BNB Smart Chain, Ethereum, BSC Testnet and Goerli, utilizing tools like Fireblocks. • Applied Cloudflare features to enhance website security and performance, incorporating relevant testing procedures. • Managed the complete project lifecycle using Agile practices (Scrum, Kanban), including sprint planning, backlog grooming, task prioritization and stakeholder communication via Jira and Notion. • Key Technologies & Tools: JavaScript, TypeScript, Java, Maven, Python, React, HTML, CSS, MySQL, Oracle, Node.js, Visual Studio Code, AWS, Azure, GitLab, Git, GitHub, Jenkins, Cypress, Selenium, Playwright, Postman, JUnit, TestNG, Allure, REST Assured, RESTful API, XML, SOAP, TestRail, TestProject, Gatling, JMeter, Fireblocks, Cloudflare, Jira, Confluence, Zapier, Notion, ClickUp, LastPass, BambooHR, Slack.
Senior QA Engineer
BairesDev 2021 - 2025
Client: RVshare (The largest RV rental marketplace in US) • Led the QA team of 4+ engineers by defining a comprehensive QA strategy, encompassing Manual and Automation testing, within an Agile (Scrum, Kanban) framework to increase test coverage. Managed full Defect Management lifecycle in Jira, Confluence and Zephyr, foster collaboration and mentor team members. • Designed & executed comprehensive test suites through functional, end-to-end, manual, exploratory, usability, database, black box & security testing, leveraging Postman, GraphQL, Datadog insights, MySQL checks and OWASP best practices; this thorough testing contributed significantly to the iOS app achieving an 8x higher conversion rate compared to the web. • Built & maintained automation frameworks in JavaScript, Java & TypeScript using Cypress, Selenium, Appium (iOS, Android), integrated with CI/CD pipelines (Git, Bitbucket, CircleCI), BrowserStack and LambdaTest for cross platform coverage ensuring compliance with high quality releases. • Drove Shift-Left testing, TDD and BDD adoption by crafting unit, API, integration, regression, smoke & performance tests (JMeter, Gatling, k6) using AI tools (Claude, ChatGPT, Cursor, GitHub Copilot) to optimize test design, reducing critical production defects by 40% through rigorous attention to detail. • Key Technologies & Tools: Jira, Confluence, Zephyr, Postman, GraphQL, Datadog, MySQL, OWASP, iOS, Android, JavaScript, Java, TypeScript, Cypress, Selenium, Appium, Claude, ChatGPT, Cursor, GitHub Copilot, Cucumber, Gherkin, Git, Bitbucket, CircleCI, BrowserStack, LambdaTest, JMeter, Gatling, k6, Swift, Xcode, TestFlight, Sourcetree, GitHub, Insomnia, Visual Studio Code, Figma, Mixpanel, Firebase, AppsFlyer, Slack, Loom.
Senior QA Engineer
ThoughtWorks 2020 - 2021
• Acted as QA Engineer and Architect, Product Owner, Project Manager and Business Analyst, shaping end-to-end test strategy and ensuring alignment with product roadmaps. • Led a cross-functional QA team of 4+ engineers, embedding Scrum, Kanban, TDD and BDD practices that increased automated test coverage to 90% and slashed regression cycles by 50%. • Designed and implemented comprehensive test suites (unit, automation (Selenium, Cypress, Playwright, Pytest), E2E, regression, smoke, integration, exploratory, cross-functional and A/B testing), uncovering critical defects before production. • Collaborated with developers to review unit tests, refine user stories, triage bugs and manage technical debt, improving sprint predictability by 30%. • Orchestrated sprint planning, backlog grooming and retrospectives in Jira, Confluence, driving continuous process enhancements and stakeholder transparency. • Applied SEO best practices and analytics strategies (Google Analytics, Adobe Analytics, Google Tag Manager) to boost e-commerce engagement by 25%. • Key Technologies & Tools: JavaScript, TypeScript, Java, Maven, Python, React, HTML, CSS, MySQL, Oracle, .NET, Node.js, AWS, GitLab, Git, Jenkins, Selenium, Cypress, Playwright, Pytest, Postman, JUnit, TestNG, Allure, REST Assured, RESTful API, XML, SOAP, Kibana, Grafana, Google Data Studio, Google Tag Manager, Google Analytics, Adobe Analytics, Jira, Confluence, Contentful, WordPress, Drupal, Gatling, JMeter, Visual Studio Code, Slack, Webex.
Senior QA Engineer
Independent Consultant 2015 - 2020
• Delivered QA and project management services for 8 clients across fintech, e-commerce, healthcare and SaaS, reducing critical defects by 50% and accelerating release cycles by 40% in average. • Architected and implemented robust automation frameworks (Cypress, Selenium, Playwright, Appium, Pytest) in JavaScript, TypeScript, Java and Python, integrating with CI/CD pipelines (Jenkins, GitLab) to ensure consistent, high-quality releases. • Developed and launched 8 responsive websites (Drupal, WordPress, React) with tailored SEO strategies that boosted organic traffic by an average of 35% and improved lead conversion by 20%. • Planned and executed diverse testing scopes, unit, E2E, regression, smoke, integration, exploratory, A/B and cross-functional (performance via Gatling & JMeter, security, scalability, compatibility, usability, accessibility), for both web and API projects. • Advised startups and SMEs on digital marketing, social media growth and online advertising, delivering campaigns that achieved up to 5x ROI. • Conducted market research and go-to-market planning for product launches in North America, Europe and Latin America, supporting clients’ market entry and fundraising efforts. • Key Technologies & Tools: JavaScript, TypeScript, Java, Maven, Python, React, HTML, CSS, PHP, MySQL, Oracle, .NET, C, C#, C++, Node.js, Visual Studio Code, Salesforce, AWS, GitLab, Git, GitHub, Jenkins, Cypress, Selenium, Appium, Playwright, Pytest, BrowserStack, Postman, TestCafe, JUnit, TestNG, Allure, REST Assured, RESTful API, XML, SOAP, Kibana, Grafana, Google Data Studio, Google Tag Manager, Google Analytics, Adobe Analytics, Jira, Confluence, TestRail, TestProject, Gatling, JMeter, Slack.
QA Engineer
EspacioCuba 2012 - 2015
• Defined and validated functional requirements for the national real-estate portal and agency websites, writing and executing test plans to ensure 100% coverage. • Managed office network infrastructure, provided support and maintained a high availability of internal systems. • Employed data analytics and BI tools to surface usage insights, enabling targeted feature enhancements and process refinements. • Key Technologies & Tools: Wordpress, PHP, Symfony, Linux, Apache, HTML, CSS, JavaScript, Ajax, MySQL, SQL, RUP.
QA Engineer
University of Computer Sciences 2008 - 2012
• Led student teams as Project Manager for significant academic software projects within the university environment. • Managed the development lifecycle of a Medical Genetics Computer System (PHP, Symfony) designed to manage patient data for genetic diseases. • Served as Project Manager for EPIGEN, a statistical analysis tool for Genetic Epidemiology research, facilitating the study of genetic and environmental factors in complex diseases. • Worked as QA Engineer defining and implementing systematic activities and testing plans (Functional, Regression, Usability, Compatibility, Security, Performance) using RUP methodology principles across various software projects. • Key Technologies & Tools: PHP, Symfony, Linux, Apache, HTML, CSS, JavaScript, Ajax, MySQL, SQL, Java, RUP.
Skills
agile
ai
blockchain
crypto
finance
fintech
java
javascript
project-manager
python
scrum
typescript
web3
quality-assurance
english
spanish