Principal Agentic SDET Engineer

Principal Agentic Software Development Engineer in Test – Full Stack

We are looking for a full-stack Principal Software Development Engineer in Test to join us in validating our security products and associated platforms. The successful candidate will be a self-starter with an automate-first and AI-first mindset , ready to validate complex test environments with many touch points across UI, API, services, cloud platforms, integrations, data, and third-party systems. This role requires someone who can combine deep hands-on engineering capability with technical leadership, using modern automation, CI/CD, observability, and AI-enabled engineering practices to improve quality, speed, reliability, and release confidence. A positive attitude, strong ownership mindset, and willingness to learn, coach, and share knowledge are essential.

Mimecast provides cyber security that helps thousands of organizations worldwide make email and messaging safer, restore trust, and bolster cyber resilience. We help organizations stand strong in the face of cyberattacks, human error, and technical failure.

At Mimecast, Principal Software Development Engineers in Test are responsible for: Providing technical leadership and coaching/mentoring other engineers on the team to deliver testing for large projects and/or ongoing product efforts. Acting as a senior technical voice for Quality Engineering across product, platform, architecture, development, DevOps, and security teams. Taking initiative to drive continuous improvement through monitoring, tooling, automation, process improvements, and engineering best practices. Bringing an AI-first mindset to quality engineering by identifying practical ways to use AI to improve test design, test automation, code review, defect analysis, test coverage, documentation, and engineering productivity. Standardising the agents to build QE process as a QE Engine. Helping teams adopt AI-enabled engineering practices safely and effectively, ensuring AI is used to accelerate delivery while maintaining quality, security, and engineering discipline. Building out test plans to cover new areas of functionality, ensuring all necessary functional and non-functional testing is performed. Contributing to the planning, estimation, and refinement of stories, epics, and design changes as part of an Agile Scrum team. Refining acceptance criteria into testable units and converting those into automated tests that execute efficiently and reliably. Using AI-assisted tools, to accelerate acceptance criteria analysis, test scenario generation, edge-case discovery, and automation development. Integrating automated tests with CI/CD pipelines and ensuring successful automation as part of the standard build and release process. Driving continuous testing practices across the delivery lifecycle, ensuring fast, reliable feedback to engineering teams. Reporting, reproducing, and helping development resolve defects, with emphasis on troubleshooting, root cause analysis, and prevention of similar issues in the future. Using logs, code, telemetry, dashboards, traces, and AI-assisted analysis techniques to investigate defects and identify systemic quality issues. Contributing to design and code reviews for product and test code. Coaching engineers on testability, automation design, coding standards, maintainability, and quality-focused engineering practices. Promoting quality as a shared engineering responsibility, not just a downstream testing activity.

Required Skills / Experience: 10+ years of experience as a Software Development Engineer in Test (or similar role) Significant experience in building AI QE process recently. Engineering / Computer science degree or equivalent experience Extensive experience test planning and breaking down stories/requirements into testable units 6+ years of significant test automation work, validating both back-end and front-end interfaces in at least one high-level object-oriented language, including: Extensive experience automating business logic in the services layer (RESTful API, SDK, or CLI, as appropriate) Proficiency in validating contract, functionality, correctness, and performance of REST API endpoints Familiarity with BDD tools like Cucumber, Jasmine, or equivalent Clear understanding of how to manage risk through negative testing, boundary/limits testing, load/soak testing, and other test aspects as appropriate, including system integration, performance/scale, security Solid object-oriented programming skills and experience automating in Java or similar

Substantial experience in validation of UI-functionality and rendering, End-to-End testing, and UAT scenarios Extensive knowledge of Cypress with demonstratable experience in Protractor / Selenium Knowledge of Web Browsers, HTML, CSS, JavaScript, TypeScript, Angular, JSON, XML, integration with APIs, web servers Great knowledge of testing design patterns - for example, the Page Object Model

4+ years of experience as a technical leader of test projects and test teams Top notch coding skills, provision at conducting effective code reviews and coaching the team to raise their coding proficiency Extensive experience with CI/CD and Continuous Delivery model using Jenkins (or similar) Working knowledge of public cloud, especially AWS, and how to execute testing in an efficient, cost-effective manner in that environment Solid DB understanding (types, schemas, SQL queries, basic operations) and ability to incorporate database-side validation into automated tests Experience with multithreading, concurrency, SaaS, and multi-tenant architectures Proven ability to integrate with and automate using third party APIs (e.g., Google, Microsoft, Amazon etc) Experience with observability, monitoring, synthetic testing, chaos engineering, disaster recovery testing, or production-readiness validation. Experience using AI tools such as GitHub Copilot, Cursor, ChatGPT Enterprise, Atlassian Intelligence/Rovo, You.com, or similar platforms to improve engineering productivity. Experience creating or improving quality dashboards, shift-left metrics, escaped defect analysis, automation reliability metrics, or engineering productivity insights. Experience with contract testing, service virtualisation, test data management, or intelligent regression selection. Some working knowledge of Microsoft Exchange, Office365, Azure Active Directory, and Windows Server

AI-First Engineering Expectations The successful candidate will be expected to bring an AI-first but engineering-led mindset . This means being able to identify where AI can genuinely improve engineering outcomes, while maintaining strong technical judgement, quality standards, and security awareness. This includes: Using AI to accelerate repetitive or analysis-heavy engineering tasks. Applying AI to improve test design, scenario coverage, code quality, defect diagnosis, and documentation. Helping teams move from ad hoc AI usage to repeatable, trusted engineering workflows. Coaching engineers on where AI is useful, where it is risky, and how to validate AI-generated output. Measuring the impact of AI adoption through productivity, quality, reliability, and speed-of-feedback improvements. Ensuring AI usage supports secure, responsible, and compliant engineering practices.

LI-GK1 Belonging at Mimecast

Cybersecurity is a community effort. That’s why we’re committed to building an inclusive, diverse community that celebrates and welcomes everyone – unless they’re a cybercriminal, of course.

We’re proud to be an Equal Opportunity and Affirmative Action Employer, and we’d encourage you to join us whatever your background. We particularly welcome applicants from traditionally underrepresented groups.

We consider everyone equally: your race, age, religion, sexual orientation, gender identity, ability, marital status, nationality, or any other protected characteristic won’t affect your application.

Due to certain obligations to our customers, an offer of employment will be subject to your successful completion of applicable background checks, conducted in accordance with local law.

It is unlawful in Massachusetts to require or administer a lie detector test as a condition of employment or continued employment.