Senior Software Development Engineer in Test (SDET)

Summary: Topstep operates a real-time futures trading platform (TopstepX). Here, correctness isn't cosmetic: a defect in order handling, market-data delivery, or a balance/P&L calculation can cost a trader real money. We're hiring a Senior SDET to drive test automation across the platform — building the frameworks, shaping coverage decisions, and raising the quality bar alongside our existing SDETs. We lean heavily on AI-assisted test generation to produce broad, meaningful coverage at scale, and you'll help extend that capability. You'll partner with product engineering teams to design for testability early, automate the journeys that matter most, and strengthen the testing practice across the group. This role suits a strong technical tester who thinks in systems and can build scalable test infrastructure while mentoring others. Key Responsibilities Drive test automation across API, UI, and end-to-end — shaping where automated coverage delivers the most value against execution time and maintenance cost. Use and extend our AI-assisted test-generation tooling to produce and maintain broad, verification-focused coverage — applying judgment to curate, validate, and prune what the models generate rather than trusting it wholesale. Build and maintain scalable test frameworks and infrastructure that run in CI/CD, including for real-time paths: order lifecycle, market-data streams over WebSocket, and financially material calculations. Partner with product and engineering early to define testability requirements and quality standards, rather than validating after the fact. Lead by example on test code quality — clean, maintainable, well-documented, and a model for the team. Own the signal from the test suite: triage failures fast, keep flakiness low, and make results and quality metrics visible and trustworthy to engineering. Surface and drive resolution of quality gaps, systemic testing weaknesses, and test-related technical debt. Mentor engineers and SDETs on automation patterns, AI-assisted testing workflows, non-functional testing (performance, load, resilience), and a quality-first mindset. Required Qualifications and Key Competencies 5 + years in software testing with a strong focus on test automation and framework development. Expert programming skills; writes production-quality test code in TypeScript. Hands-on experience building test automation frameworks from scratch (Playwright preferred; Cypress, Selenium, or similar also relevant). Comfort using AI/LLM-assisted tooling to accelerate test creation and verification, with the judgment to validate and curate generated output rather than accept it at face value. Strong API and real-time testing: RESTful services and WebSocket/streaming systems, with a solid grasp of backend testing patterns. Solid grasp of our stack — a React/TypeScript front end and C#/.NET backend services, plus databases and the service architecture behind them — enough to test it deeply. CI/CD experience integrating automated tests into deployment pipelines (GitHub Actions). Proven ability to design test strategies that balance coverage, execution time, and maintenance overhead. Strong debugging across the full stack — frontend, backend, database, and infrastructure. Excellent communication; can advocate for quality and influence engineering practice. Preferred Non-functional testing experience: performance, load, and resilience. Familiarity with ArgoCD, Terraform, and Kubernetes. Experience testing trading, fintech, or other low-latency/financially sensitive systems. Contract / consumer-driven testing between services. Observability-driven testing (using logs, metrics, traces to validate behavior). Company Culture & Perks Topstep is an engaging working environment that ranges from fully remote to hybrid. We foster a culture of collaboration by keeping cameras on during meetings and maintaining a robust Slack environment for communication. Seven Company-paid Holidays and generous Family Leave. Paid time off is front-loaded. Competitive 401(k) matching, health, dental, and vision insurance are offered for full-time employees. Vacations are encouraged with a bonus for taking 5 consecutive days. Topstep offers a food and groceries budget and contributes towards health and wellness. New Hire Base Salary Range $155,000 - $190,000 annually. The compensation offered will take into account the internal compensation structure and may vary depending on the candidate's geographic region, job-related knowledge, skills, and experience, among other factors. This position is eligible for a performance-based bonus as provided by the plan terms and governing documents. Equal Opportunity Employer Topstep is an Equal Opportunity Employer. We are committed to fostering an inclusive environment where all employees and applicants are valued. All qualified candidates will receive consideration for employment without regard to race, color, religion, gender, gender identity or expression, sexual orientation, national origin, age, disability, or veteran status, in compliance with applicable federal, state, and local laws. Interested in the role? Apply today with your resume! The collection, use, and handling of your data provided in response to this job posting is described further in our Privacy Policy. If you are a California resident, please review our California Notice at Collection. Notice of Use of Artificial Intelligence in Recruitment and Hiring: Notice Pursuant to 775 ILCS 5/2-102(L). Topstep LLC uses artificial intelligence ("AI") in connection with its recruitment and hiring process. Examples include, but are not limited to, AI tools used to improve job descriptions, generate interview questions, draft communications, assist with scheduling, and source candidates, as well as AI features built into third-party platforms such as LinkedIn, Indeed, and Glassdoor. Topstep will not use AI that has the effect of subjecting employees or applicants to discrimination on the basis of any protected class under the Illinois Human Rights Act.