Principal SDET (Software Development Engineer in Test)

Principal SDET (Software Development Engineer in Test)

If you have a passion for catching issues before customers do, love writing rock-solid automated tests, and want to help elevate our product quality at Paystone, this role is for you!

As a Principal SDET (Software Development Engineer in Test) you’ll define our automated test strategy, expand test coverage, and empower every engineer to ship confidently by building robust, comprehensive tests.

Reporting to: VP, Engineering

Department: Engineering

What You'll Be Doing:

Test Automation & Technical Leadership

Design, build, and maintain robust automated test suites using Jest (API / integration) and Playwright (end-to-end, cross-browser).

Review application architecture to identify risk areas and define the right test pyramid (unit integration E2E).

Establish and document coding standards for test automation; perform PR reviews to uphold them.

Investigate test failures quickly, triage defects, and collaborate with developers on root-cause analysis.

Quality Process Improvement

Champion shift-left testing: embed quality gates in every stage of the SDLC and CI/CD pipeline.

Analyze flakiness, execution time, and coverage metrics; drive continuous optimisation.

Introduce tooling (static analysis, mutation testing, visual regression, etc.) when it meaningfully boosts product quality.

Cross-Team Collaboration & Facilitation

Partner with Product Owners and Squad Leads to turn acceptance criteria into executable automated tests.

Act as a quality mentor: run workshops, pair-program on test patterns, and nurture a culture of ownership.

Review upcoming technical designs with an eye on observability and testability, providing actionable feedback early in the lifecycle.

Planning & Delivery

Estimate and prioritise test automation work in sprint planning, balancing risk and velocity.

Provide clear visibility into test coverage, defect trends, and release health to stakeholders.

Ensure test environments and data are version-controlled, reproducible, and aligned with production.

What We're Looking For:

Proven success improving product quality for SaaS solutions in an agile environment.

Deep hands-on expertise with Jest and Playwright (or similar frameworks) and solid TypeScript/JavaScript skills.

Experience integrating automated tests into cloud-based CI/CD (GitHub Actions, GitLab CI, etc.).

Strong understanding of testing strategies (TDD, BDD, contract testing, accessibility, performance).

A collaborative, solution-oriented mindset with crisp, confident communication.

Passion for mentorship and driving a culture of quality across engineering teams.

Whether you’re already a senior automation specialist or an experienced developer passionate about quality, this role lets you broaden your impact while staying deep in the code.

Let’s raise the bar on reliability — together.