Quality Engineering
Non-Functional TestingFast, secure, usable, reliable, the qualities users feel first.
Users forgive a missing feature faster than a slow, flaky, or confusing one. Non-functional Testing covers the qualities users feel first, performance, reliability, usability, compatibility, with measurable targets instead of vague hopes.
What this covers
Performance and scalability validation against explicit targets
Reliability and recovery Testing, restarts, failovers, degraded modes
Compatibility across browsers, devices, and OS versions
Usability heuristics and task-completion Testing
Non-functional requirements definition when none exist yet
The qualities users feel before they see features
Users forgive a missing feature far faster than a slow, unreliable or confusing one.
Users forgive a missing feature far faster than a slow, unreliable or confusing one. Non-functional Testing covers the attributes that determine how a product feels rather than what it does: speed, reliability, usability, compatibility, scalability, recoverability and maintainability. These are the qualities that drive churn, and they are the ones most often left without a written target.
That absence is the core problem. 'It should be fast' is not testable. 'The search results page returns in under 800ms at p95 with 500 concurrent users on a cold cache' is. A large part of this engagement is turning implicit expectations into explicit, measurable requirements, which usually surfaces disagreement between engineering, product and commercial stakeholders that was better found now than after launch.
What we cover
Performance and scalability: latency and throughput against agreed targets, and behaviour as load grows, covered in depth by Performance Testing.
Reliability and recoverability: restarts, failovers, degraded modes, and whether the system returns to a consistent state after an interruption.
Compatibility: browsers, devices, operating systems and screen classes, ranked by your real audience rather than by a generic support matrix.
Usability: task completion, error recovery and heuristic review, whether people can actually finish what they came to do.
Accessibility: WCAG 2.2 AA conformance, handled by our Accessibility Testing practice.
Security posture and maintainability: application-layer exposure, plus how easily the system can be changed without breaking.
Defining requirements where none exist
Most teams we meet have no written non-functional requirements at all.
Most teams we meet have no written non-functional requirements at all. We derive a first set from your traffic data, your users' expectations and your commercial commitments, including any SLAs you have already signed, then test against them and refine. The value is not only the test results: it is that the organisation now has agreed numbers, so the next argument about whether something is 'fast enough' has an answer.
Engagement path
How the engagement runs
Every Non-Functional Testing engagement runs the same way: understand the risk, build the thing that reduces it, prove it works, hand it over.
Requirements workshop
We turn implicit expectations into measurable targets for speed, reliability, compatibility and usability, and get them agreed in writing.
Baseline measurement
Current behaviour measured against those targets, so everyone can see the actual gap rather than argue from impressions.
Attribute-specific Testing
Load, resilience, compatibility, usability and accessibility passes, each run with the tooling and method that attribute genuinely needs.
Remediation and monitoring
Prioritised recommendations, retests to prove them, and the checks that belong in CI so regressions surface early.
Deliverables
What you get
Artefacts you keep and can run without us. Everything lives in your repositories and your tooling.
Handover pack
6 artefacts · yours to keep
A written, agreed set of non-functional requirements with numbers in them
A measured baseline showing where the product sits against each target
Compatibility results across a matrix derived from your real audience
Reliability and recovery findings, including degraded-mode behaviour
Usability findings based on task completion, not opinion
CI checks for the attributes that can regress on an ordinary commit
Self-check
Signs your team needs this
If more than one of these is true, it is usually cheaper to fix now than after the next release.
Users describe the product as slow, clunky or unreliable without filing a defect
There are no written targets for speed, uptime or compatibility
An SLA has been signed and nobody has verified the product can meet it
Compatibility support is claimed but never tested across the claimed matrix
The system recovers from failures in ways nobody has actually observed
A Senior Engineer replies within one business day. NDA first.
Questions
Frequently Asked Questions
Straight answers, written the way we'd say them on a call.
Still curious? Talk to usKeep reading
Where to go next
Non-Functional Testing rarely stands alone. These are the disciplines and resources teams pair it with most often.
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- A Senior Engineer replies, not a sales layer
- Within one business day, every time
- NDA available before you share any details
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16
Testing disciplines
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