Assumption Testing: Everything You Need to Know to Get Started

Teresa Torres argues that product teams should regularly test the underlying assumptions behind their ideas rather than whole solutions, so they can compare options quickly and drop weak ones early. She explains that an assumption is a belief that must hold for an idea to succeed, and that the more specific it is, the easier to test. She outlines five assumption categories (desirability, viability, feasibility, usability, ethical), shows how to surface and phrase assumptions, and describes four test types: prototype tests, one-question surveys, data mining, and research spikes. The piece also covers prioritizing riskiest assumptions via assumption mapping, defining success upfront, iterating after failures, and tracking results. Its value lies in giving teams a practical, low-cost discovery habit that applies at any product maturity.

01Key takeaways

• Test specific assumptions behind ideas instead of whole ideas to compare options quickly.
• Generate assumptions across desirability, viability, feasibility, usability, and ethics, rather than debating categories.
• Phrase assumptions as things customers must do for the idea to succeed, since they are easier to test.
• Prioritize assumptions that are critical to the idea but have little supporting evidence.
• Define success criteria before each test so results can be judged rather than debated.
• Start with the smallest test you can run in an hour and repeat it regularly to build the habit.

02Key sections

Why test assumptions

Comparing multiple options leads to better decisions, but teams often rush to a first idea. Testing the assumptions beneath ideas lets teams compare options without slowing down.

Defining and categorizing assumptions

An assumption is a belief that must hold for an idea to work, and the five categories help generate risk-revealing assumptions across the board. Exact category labels matter less than coverage.

Identifying and phrasing assumptions

Techniques like story mapping, walking opportunity solution tree links, and pre-mortems surface hidden assumptions. Phrase them so they must be true for the idea to succeed, and keep them specific.

Choosing and running tests

Focus on the riskiest assumptions using assumption mapping, pick a fitting test type, and define success before running it. Failed tests point to exactly what to change.

Starting small and tracking

Teams can begin with existing data or simple tools and build the habit in small daily steps. Tracking attributes like assumption, audience, criteria and results keeps learning accessible.

03From the post

“A regular cadence of assumption testing helps product teams quickly determine which ideas will work and which ones won’t. It’s one of the highest value activities we can do. And sadly, most product teams don’t do any assumption testing at all. And those that do, don’t”

04Frameworks mentioned

Summary and takeaways written by PM Atlas; quotes are short excerpts. © the original author.