Use when planning or conducting usability tests — writing test scripts, defining tasks, selecting participants, analysing findings, and turning observations into design actions
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Use when planning or conducting usability tests — writing test scripts, defining tasks, selecting participants, analysing findings, and turning observations into design actions
Usability Testing
Testing with real people is how you find out if the design works — not by looking at it, but by watching someone use it.
When to Use
After design-builder produces a working prototype
Before declaring a design complete
When the design-critic flags persona coverage gaps
When assumptions about user behaviour need evidence
Process
Step 1: Define What You're Testing
Write 3-5 task scenarios that map to the core jobs in the brief. Each task:
Starts with a realistic trigger — "You just bought a new plant and want to add it to the app"
Has a clear success condition — "The plant appears in your list with a watering schedule"
Does not tell the user how — never say "tap the + button"
Step 2: Select Participants
Recruit 5-8 participants. At minimum include:
1 person who uses a screen reader
1 person over 60
1 person who is not a native speaker of the interface language
1 person with low tech confidence
Reference inclusive-personas for the ability spectrum.
Step 3: Choose Method
Method
When to use
Minimum participants
Moderated think-aloud
New flows, complex interactions
5
Unmoderated remote
Simple tasks, large sample
8-12
Guerrilla (hallway)
POC validation, time-constrained
3-5
Accessibility audit with AT users
After build, before ship
2-3
Step 4: Write the Test Script
Welcome — explain what you're testing (the design, not them)
Background — 2-3 questions about their relationship to the problem
Tasks — present each scenario one at a time, observe silently
Debrief — "What was hardest?" "What would you change?"
Never help during a task. Silence is data.
Step 5: Analyse Findings
Classify outcomes per task:
Completed easily — no hesitation, no errors
Completed with difficulty — hesitation or errors but recovered
Failed — could not complete
Completed wrong — thought they succeeded but didn't
Severity: Critical (blocks 2+ participants), Major (significant difficulty), Minor (noticed but not impeding).
Step 6: Turn Findings Into Actions
Every finding becomes a design action: "[Severity] [What happened] → [Design action] → [Which agent handles it]"
