Testing Software Quality Characteristics
The ISO/IEC 25010 lens
ISTQB frames quality with ISO/IEC 25010, which names characteristics such as functional suitability, performance efficiency, compatibility, usability, reliability, security, maintainability and portability. The test analyst's core responsibility is functional suitability (completeness, correctness, appropriateness), supported by usability and accessibility, and usually some security and compatibility checks. Performance, reliability engineering and deep security testing normally need specialist skills, though the analyst may design functional tests that expose them.
For usability, test effectiveness (can users complete the task?), efficiency (effort/time) and satisfaction, using checklists, user observation and heuristics. Accessibility is distinct from usability: it targets people with disabilities, often against WCAG levels (A, AA, AAA) and with assistive technologies such as screen readers. Security basics for the analyst include authentication, authorization, confidentiality and integrity checks; reliability covers availability, fault tolerance and recoverability.
Traps: treating usability and accessibility as synonyms; assuming the test analyst tests every characteristic; swapping "functional correctness" with "functional suitability" (correctness is one sub-characteristic); and ignoring that non-functional tests often need environments, tools and skills outside the analyst's remit.
Worked example. For an online checkout: usability - a checklist for completing a purchase in a set number of steps; accessibility - verify WCAG 2.1 AA labels and keyboard navigation on the payment form; security - test session timeout and password policy; performance - raise to the performance specialist, supplying realistic functional scenarios.
Rule of thumb: the analyst owns functional and usability/accessibility depth and contributes functional scenarios to non-functional testing.