OAT Tester

Hybrid: Predominantly work from home - on-site in Croydon/M3 Corridor when required.

Start Date: June

Due to nature of this role, we require the successful candidate to be able to obtain high level security clearance. You must have lived permanently in the UK for the last 5+ years to be eligible. You must also hold a British Passport only.

We are seeking a highly skilled Operational Acceptance Test (OAT) Engineer to oversee and lead the end-to-end operational testing process. The ideal candidate will have a strong background in operational readiness, system performance and production environment validation on cloud-based services.

• Act as a senior member of the team, taking lead on Operational Acceptance Testing (OAT) process, ensuring systems meet operational and business requirements before deployment.
• Define OAT test strategies, plans and criteria to validate infrastructure, system reliability, failover mechanisms and non-functional requirements.
• Collaborate with Dev Ops, Infrastructure and Release Management teams to ensure smooth transition from development to production on AWS cloud.
• Conduct cloud-based resilience, failover, backup and recovery testing.
• Ensure compliance with SLAs, security policies and disaster recovery procedures.
• Identify, document, and manage defects and issues, ensuring timely resolution.
• Provide leadership and mentoring to junior testers and team members.
• Generate detailed reports and dashboards on OAT progress, results, and risk assessments.

• Experienced in Operational Testing.
• Deep understanding of OAT methodologies, including but not limited to the following core areas:
  • Build verification
  • Alert and Monitoring
  • Backup and Restore
  • Resilience and Recovery
  • Logging, Audit and House Keeping
  • Release Management
  • Work Instructions
  • OWASP "top ten" security tests
• Experience with CI/CD pipelines, Jenkins, and test automation frameworks.
• Knowledge of cloud platforms (AWS/Azure), infrastructure monitoring, and IT service management.
• Familiarity with databases, Linux environments, and network protocols.
• Experience in working with Agile & Dev Ops methodologies.
• Strong analytical and problem‑solving skills with attention to detail.
• Excellent communication and stakeholder management abilities.

• Experience with performance testing tools (JMeter, Load Runner, etc.).
• Knowledge of Kubernetes, Docker, or containerised environments.
• Certification in ISTQB, ITIL, or AWS/Azure Cloud services.

• 25 days annual leave + bank holidays
• Up to 5% employer matched pension contribution
• Work on meaningful government projects
• Numerous health & insurance benefits
• Fantastic culture with regular social events

CACI is proud to be an equal opportunities employer. Embracing the diversity of our people, we are on a journey to build a truly inclusive work environment where no one is treated less favourably due to ethnic origin, age, gender, veteran status, religion or belief, sexual orientation, marital status, and disability or health condition, actively working to prevent discrimination.

As a Disability Confident employer, we will:

• Provide reasonable adjustments in the recruitment process where requested (contact a member of the recruitment team on  to discuss individual requirements further).
• Offer people with health conditions and disabilities, meeting the minimum criteria for a role, an interview.