Practice : Non-functional Requirement Testing

Purpose and Strategic Importance

Non-functional Requirement (NFR) Testing validates how a system performs under specific conditions beyond just functional correctness. It encompasses critical attributes like performance, security, scalability, usability, reliability, and compliance - all of which impact the overall user experience and operational integrity.

Proactively testing for NFRs enables teams to build systems that not only work, but work well - delivering value at scale, securely, and under pressure. It supports resilient architecture and future-proofed delivery.

Description of the Practice

  • NFR testing verifies system attributes like performance, scalability, availability, maintainability, and security.
  • Tests are designed around service-level objectives (SLOs), regulatory expectations, or user experience benchmarks.
  • Approaches include load testing, chaos testing, accessibility audits, security scanning, and uptime monitoring.
  • NFR tests are executed during CI/CD, before major releases, or on a scheduled basis.
  • Results are shared across teams and influence product decisions and architectural improvements.

How to Practise It (Playbook)

1. Getting Started

  • Define the key NFRs for your service or product - ideally tied to business risk or customer expectations.
  • Collaborate with product, security, and platform teams to translate NFRs into testable criteria.
  • Select tools and metrics aligned to each NFR type (e.g. response time, accessibility score, uptime %).
  • Include basic NFR tests in pre-release validation or CI/CD pipelines.

2. Scaling and Maturing

  • Establish baselines and targets for each NFR - such as response times under load or recovery time objectives.
  • Automate tests and include NFR test gates in release workflows.
  • Make test results part of observability dashboards and service health reports.
  • Continuously refine NFR coverage as systems and user expectations evolve.
  • Include NFR test insights in architectural and investment decisions.

3. Team Behaviours to Encourage

  • Treat non-functional quality as a shared responsibility across disciplines.
  • Regularly review NFR performance alongside functional outcomes.
  • Use testing insights to prioritise tech debt reduction or scaling improvements.
  • Include NFR outcomes in retrospectives, postmortems, and OKRs.

4. Watch Out For…

  • Defining vague NFRs without measurable outcomes.
  • Only testing NFRs in staging - production-like conditions matter.
  • Siloed responsibility for NFRs - it should not be “just security” or “just ops.”
  • Over-prioritising functional test coverage at the expense of NFR health.

5. Signals of Success

  • Systems meet defined performance, security, and resilience expectations.
  • NFR coverage is visible, automated, and improving over time.
  • Failures in NFR tests lead to real improvements - not ignored results.
  • Product planning and architectural reviews include NFR discussions.
  • Customers trust the system's stability, performance, and compliance.