Assumption testing
Last reviewed
Assumption testing is the practice of identifying the beliefs a solution depends on and checking the riskiest ones with small tests before building. Teresa Torres groups these beliefs into desirability, viability, feasibility, usability and ethical assumptions. It is the mechanism that connects solutions to evidence in an Opportunity Solution Tree.
The five categories
Sorting assumptions by type makes it much harder to miss a whole class of risk. Teams that only ever test desirability ship things customers want but cannot afford to run, or cannot legally offer.
- Desirability: do customers actually want this?
- Viability: does it work for the business commercially and strategically?
- Feasibility: can we build and operate it with what we have?
- Usability: can people figure out how to use it?
- Ethical: could this cause harm, and are we comfortable with the trade-offs?
Mapping assumptions before testing them
The usual approach is to list every assumption a solution rests on, then place each one on two axes: how much it matters if it is wrong, and how much evidence currently supports it. The top-right corner, important and unevidenced, is where testing starts. Most assumptions never need a test at all.
Frequently asked questions
What are the five assumption types in product discovery?
Desirability, viability, feasibility, usability and ethical. The categories come from Teresa Torres's continuous discovery work and exist to stop teams from testing only whether customers like an idea while ignoring whether it can be built, sold or safely operated.
Related terms
- ExperimentAn experiment is a small, fast test that checks a specific assumption behind a solution before the team commits to building it.
- SolutionA solution is a specific thing a team could build or change to address one opportunity in an Opportunity Solution Tree.
- EvidenceEvidence is the recorded observation that supports or undermines a claim in an Opportunity Solution Tree.
See how assumption testing fits the whole tree
The full guide covers all four layers and how they connect.