Applications Test Engineer

Test Engineer - Derby, East Midlands

Ref: 151Wednesday 16 September 2026

Competitive Salary

Salary: Competitive Salary| Derby - Onsite | Contract - 6 months initially | Flexible Working

Security Clearance: Minimum SC clearance required and have it cleared already; DV highly desirable

We're recruiting for a Applcations Test Engineer to join a growing and ambitious team at a pivotal stage in its journey.

Want to be part of a business that is disrupting the national security market? Our client is a fast-growing UK sovereign technology company delivering innovative encryption and secure communications solutions to some of the country's most demanding customers. Combining deep technical expertise with an agile, customer-focused approach, they are challenging the status quo and proving that world-class capability can come from a dynamic and ambitious SME.

What We're Looking For:

  • 5+ years’ commercial experience in software or applications testing.

  • Strong experience testing Windows desktop applications, ideally within a .NET environment.

  • A solid understanding of functional, system, regression and integration testing.

  • Experience writing and executing structured test cases and test procedures.

  • Strong skills in defect investigation, troubleshooting and root cause analysis.

  • Experience testing UI/UX, user workflows and application functionality.

  • Good networking knowledge across TCP/IP, routing, switching, VLANs, DHCP, DNS and VPNs.

  • Practical understanding of SNMP and network device management.

  • Experience using Wireshark or similar packet-analysis tools.

  • Strong written and verbal communication skills, with the ability to produce clear technical documentation and test reports.

  • A methodical, analytical approach and excellent attention to detail.

  • The ability to work independently while collaborating effectively with software developers and engineering teams.

Key Responsibilities: 

  • Create, review and maintain test plans, test procedures and test cases for Windows desktop applications.

  • Plan and execute functional, system, regression and integration testing.

  • Test applications used to configure, monitor and manage secure networking devices.

  • Validate software requirements and ensure requirements traceability throughout the development lifecycle.

  • Assess UI, UX and end-to-end user workflows to ensure applications are intuitive, reliable and fit for purpose.

  • Identify, reproduce, investigate and document software defects and technical issues.

  • Perform troubleshooting and root cause analysis, working closely with developers and engineers to resolve issues.

  • Validate communications between software applications and network-connected hardware.

  • Test SNMP functionality and network device management features.

  • Analyse network traffic and communications using Wireshark and similar tools.

  • Record test results, observations and defects accurately and maintain clear technical documentation.

  • Support software releases, acceptance testing and customer-facing validation activities.

  • Contribute to improving testing processes, methodologies and quality standards.

  • Support the development of automated testing and contribute scripting or automation ideas where appropriate.

  • Work collaboratively with software developers, systems engineers and product stakeholders to ensure high-quality software delivery.

What's on offer:

  • 25 days annual leave 

  • Company pension 

  • 4x Death in service

  • EV car scheme 

  • Benefit platform with high street discounts 

If you have the experience we are looking for and you think you will succeed within this industry and role, apply today.

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