Senior Software Development Engineer in Test (SDET)

About the role

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.