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Plate RES·016 · Research methodGrid H1 · Rev. 2026-08-14

Guerrilla Testing

Fast, informal testing with whoever is available, which is far better than no testing and worse than proper recruitment.

Research methodCraft conventionFoundational

Definition

Guerrilla testing recruits participants opportunistically, typically for short sessions with a rough prototype. It trades representativeness for speed and cost.

Craft convention. True because the industry converged on it. Breaking it costs familiarity, not correctness.

On this plate
  1. 1Definition
  2. 2What it is good for
  3. 3Running one in an afternoon
  4. 4In practice
  5. 5Local chart
  6. 6Continue from here

Reach for this when

  • You need an answer this week.
  • The question is about comprehension rather than domain fit.
  • No research budget exists.
  • A decision is stuck on opinion and any evidence would unstick it.

Common mistakes

  • Presenting convenience-sample findings as representative.
  • Testing domain-specific tasks with non-domain participants.
  • Skipping proper research because this feels sufficient.
  • Running it near the office, where half the sample works in software.

What it is good for

  • Catching obvious comprehension failures in labels and copy.
  • Testing a single flow quickly during a sprint.
  • Building the team's habit of watching people use things.
  • Settling internal disagreements cheaply.

Running one in an afternoon

  1. 1

    Pick one question

    Not a sweep of the product. One flow, one decision, something you could act on tomorrow.

  2. 2

    Write three tasks and a screener sentence

    The screener is one question that rules people out: whether they have ever booked travel online, for instance.

  3. 3

    Buy the coffee first

    Ask for ten minutes, say what it is for, and hand over something small. Interrupting people is a cost you should pay for.

  4. 4

    Keep sessions to ten minutes

    Two tasks and a closing question. Anything longer belongs in a recruited study.

  5. 5

    Write it up the same day

    Five to eight participants, then a short note that states where they came from, so nobody quotes it as representative later.

In practice

  1. i.

    Settling an internal argument

    Common use

    Two teams disagreed for a fortnight about a label. Six strangers in a cafe resolved it in ninety minutes, because neither wording meant what either team assumed.

Local chart

RES·016 · Region IV · Grid H1

This entry and the entries it is stated to connect with. Each line is labelled with what the connection means.

Curse of KnowledgeBIAS·008 · PRINCIPLES BEHIND THISSurvivorship BiasBIAS·010 · PRINCIPLES BEHIND THISUsability Test ScriptTPL·007 · OFTEN USED WITHUserTestingTOOL·019 · OFTEN USED WITHUsability TestingRES·001 · ALTERNATIVE APPROACHFive-Second TestRES·008 · RELATED CONCEPTPrototyping FidelityFLOW·005 · RELATED CONCEPT

Continue from here

Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.

Principles behind this

The reasoning this solution is an application of.

Often used with

These usually appear in the same screen or the same decision.

Alternative approach

A different answer to the same problem, with a different cost.

  • Usability TestingRES·001 · Research method

    Cheaper and faster, with a sample you did not choose.

Related concept

Connected closely enough to change how you apply this.