Senior Software Development Engineer in Test

Who you are

• At a Senior level at Semble, we will expect you to be mostly autonomous in your scope and to own and solve complex tasks or lead projects independently. You will work with peers from different functions and have an impact across department. You may be in a mentoring role for more junior team members and should be able to influence effectively and lead by example throughout the company
• 5+ years of professional experience as SDET or Test Automation Engineer
• A strong track record of designing, building, and evolving automation frameworks that are reliable, maintainable, and easy for engineers to adopt
• Hands-on experience building AI-augmented or agentic quality workflows, not only using tools such as Cursor or Claude to generate test code
• A pragmatic approach to AI adoption, with awareness of data privacy, security, clinical safety, cost, and false-positive risks
• Strong commercial experience with TypeScript-based automation frameworks. Playwright experience is highly desirable
• Experience with test coverage strategy and applying the testing pyramid to reduce unnecessary E2E testing
• Experience with write unit, component, API and integration tests
• Experience with performance testing tools, such as k6, is desirable
• Knowledge of non-functional testing, including performance, accessibility, security, and reliability
• Exposure to DevOps tools and cloud infrastructure, including Jenkins, Bitbucket, Datadog, and AWS
• Strong written and verbal communication skills, with the confidence to represent the SDET function, challenge assumptions, and defend quality in release discussions

What the job involves

• The Senior SDET, Frameworks role will lead the evolution of Semble’s test automation capability and help make quality a shared engineering discipline. You will:
• Lead the transformation towards a Quality Agent System, using AI agents and deterministic automation to continuously identify coverage gaps, generate and maintain tests, detect flaky tests, support exploratory testing, and surface reproducible defects
• Design safe, maintainable agent workflows with clear responsibilities, isolated execution, human review, and appropriate controls. Agents should assist engineers and SDETs, not replace human judgement or merge their own changes
• Establish the foundations required for this system, including a stable Playwright framework, reliable CI integration, ephemeral test environments, test data management, quality observability, and structured test knowledge
• Set up meaningful quality gates in CI and PR workflows, including coverage validation, framework conventions, high-risk code checks, and actionable failure reporting
• Rationalise our overcrowded E2E suite by identifying tests that belong at unit, API, or integration level, keeping E2E focused on critical user journeys
• Build and maintain a cross-layer coverage map and risk-based defect view, helping teams understand where quality gaps exist and where automation investment will have the greatest impact
• Expand test coverage and surface quality gaps earlier in the development lifecycle, including through test scenario generation, mutation testing, and AI-assisted exploratory testing
• Conduct proof-of-concepts for non-functional testing, including performance, accessibility, security, and reliability testing
• Contribute to company-wide quality strategy, tooling decisions, quality metrics, and shift-left adoption alongside the wider SDET and Engineering teams
• Coach engineers and SDETs on effective test design, the testing pyramid, Playwright, and contributing to the shared framework

Benefits

• The great feeling coming with knowing you do something that matters: improving healthcare!
• Autonomy and ownership – we’ll set the vision and share the context, then we trust you to run with things – that’s the reason we hire you!
• 36 days holiday a year (including BH), that we will expect you to actually take so you can recharge and rest
• Hybrid & flexible work environment – work from anywhere in the UK, with also some flexibility to work across Europe. You decide how much or how little you go to the office
• Get the tech you need - You will get the latest MacBook and take your pick across a wide range of equipment to set up your home office ergonomically
• Work alongside an inspiring team – our two founders have started Semble after a successful startup exit, and your future colleagues are all knowledgeable and innovators in their field
• Fantastic office space in Central London, right outside Monument - with a roof terrace, weekly animations, loads of natural light, and cute doggies!
• The usual free bits coming with nice offices (barista coffee, tea, fruits, happy hours and activities...).
• Company Equity - We appreciate and recognise all of our employees’ contributions, so everyone is eligible for Semble share options!
• Comprehensive health & wellbeing support – including private health insurance, and mental health support and free therapy sessions through Oliva.