Software Development Engineer in Test (SDET)

​Charterhouse is representing a confidential client building a next-generation AI-enhanced Network Operating System (NOS) from the ground up. This is a greenfield opportunity free from legacy constraints and uncompromising on quality. The opportunity is open to a Principal SDET ready to lead testing strategy or a Senior SDET focused on scalable automation. The role provides the chance to shape how modern networking software is validated at scale.

About the role

The SDET plays a key role in ensuring networking software performs reliably in real-world, not only in controlled environments but also under the pressure of massive data flows and complex deployments. This role provides a rare opportunity to work on a brand-new NOS platform, free from legacy constraints, where quality is built in from the start and testing is treated as a first-class engineering discipline.

As a Principal SDET, responsibilities include defining and implementing the testing strategy for networking software powering global infrastructure, working directly with the CTO to architect systems that validate everything from microsecond-level packet processing to network-wide protocol convergence.

The position involves developing automated testing systems that can keep pace of a fast-moving, next-generation NOS. Core activities include writing tests to ensure protocols like BGP, OSPF, and MPLS perform as expected and meet with industry standards. The role requires direct involvement with CI/CD pipelines to identity and resolve issues before they reach production, as well as designing realistic network simulations to test system limits. Close collaboration with engineering teams to build quality checks directly into new features from the start.

About you

The ideal candidate for SDET should have strong Python programming skills with the ability to write test code that is clean, extensible, and maintainable. A solid grasp of networking fundamentals is essential, along with experience using test frameworks like Pytest or Nose. Proficiency with Linux systems, containers, virtualization, and OS-level debugging is required, as well as experience with CI/CD experience and a tenacious approach to debugging.

For Principal-level candidates, a minimum of 8 years of hands-on experience in testing or quality engineering is expected, ideally with a background in large-scale systems. A strong understanding of networking, advanced Python skills and proven expertise in testing distributed environments effectively are essential. Knowledge of performance testing and experience building CI/CD pipelines for software that needs to run reliably in production are also highly valued. The role requires the capability to design test frameworks that simplify complex validation scenarios and to build network simulations that reflect production-level complexity. Candidate must be able to debug deep system interactions and design testing approaches that provide actionable insights into system behavior. Experience in establishing scalable quality processes is advantageous.

Additional strengths include experience validating routing protocols in production environments, stress-testing systems at scale and familiarity with infrastructure-as-code (IaC) tools such as Ansible or Terraform. Network simulation expertise using GNS3, EVE-NG, or custom frameworks is also highly desirable. Contributions to open-source testing frameworks and a history of building quality-focused engineering cultures are strong differentiators. Alongside the technical skills, excellent verbal and communication skills in English are essential.