In developing your solution, you made choices based on intuition, observation or conviction.

These assumptions are called "critical" if the viability of your solution is at stake. If your critical assumptions turn out to be false, this can be fatal to your project: your solution could be rejected by users.

To put all the chances on your side, prepare a test to validate or invalidate your critical assumptions.

Step 1:
Explain the critical assumptions of your project. As an example, one of the critical assumptions of the Waze app is that users would accept to share their GPS position.

Step 2:
For each critical hypothesis : who to question? Make sure the number and diversity of your test population is sufficient to be representative.
- What feedback would validate this critical hypothesis?
- What methods will you choose? a call? a text message? a questionnaire? a street interview? a question or a proposal on social networks? a simulation of use?

Step 3 :
Organise the concrete conduct of the tests of each critical hypothesis (Who? What? When?...) and plan the results analysis session.

NB: To collect feedback from the field, you can rely on the following tips :  
- Ask open-ended questions, and follow up if necessary.
- don't jump to conclusions!
- question the different aspects of the experience: functional, emotional, social...
- document the reactions as much as possible: verbatims and behaviours.