Every product rests on a collection of assumptions. The team believes users want a specific feature. The team believes users experience a problem in a certain way. The team believes users will change their behavior if the product makes it easy enough. These beliefs feel reasonable — they’re based on experience, observation, and judgment. But until they’re tested against real user behavior and real responses, they’re still assumptions, and untested assumptions in product development have a way of becoming expensive problems after launch.
A 2024 Harvard Business Review study found that conventional assumption testing approaches — particularly standard prototype testing — often fail to yield useful insights in complex product ecosystems, where the product’s value depends on interactions with other tools, contexts, or behaviors that prototypes can’t replicate. This finding points to something product teams encounter consistently: the method used to test an assumption shapes what the test can reveal. A technique that validates one type of assumption may be completely blind to another type.
Derribar Ventures builds and develops products for digital platforms, with a particular focus on research and validation before significant development investment is committed. Derribar Ventures has found that the type of assumption being tested determines everything else about how the research should be designed. The four techniques below are how Derribar Ventures Limited tests product assumptions in ways that are specific to the type of assumption being examined.
Why the Right Technique Matters as Much as the Question
Not all product assumptions are the same kind of thing. Some assumptions are about desirability — whether users want what’s being built. Some are about usability — whether users can accomplish what the product is asking them to do. Some are about behavioral change — whether users will actually shift their existing habits in the way the product requires. And some are about context — whether the product fits into the user’s actual environment in the way the team imagined.
Each assumption type requires a different research technique to surface meaningful evidence. A technique designed to assess desirability will produce weak evidence about behavioral change. A technique optimized for usability will miss context assumptions entirely. Applying the right technique to the right assumption type is what makes user research change product decisions rather than simply confirm them.
Derribar Ventures Limited treats technique selection as a first step in the research process, not a default — the four techniques below are matched to the specific assumption types they’re best designed to test.
Technique 1: Contextual Inquiry for Context and Behavior Assumptions
Contextual inquiry puts the researcher alongside the user in their actual environment — watching how the user currently solves the problem the product intends to address, where that problem actually occurs. It’s an observation in the real world, combined with a structured conversation about what the researcher is seeing.
This technique is particularly suited to testing context assumptions — the assumptions the team has made about when, where, and how the user will interact with the product. Those assumptions are often invisible in lab-based testing because the lab environment removes exactly the conditions that would reveal them. A user who performs a task smoothly in a quiet lab setting may face completely different constraints when trying to perform the same task on a phone with a child in the background and twenty seconds between interruptions.
Derribar Ventures uses contextual inquiry to surface the gap between the product’s assumed use context and the user’s actual use context — findings that tend to be the most surprising, because they reveal that the product’s design is often optimized for a situation the user rarely encounters.
What Contextual Inquiry Reveals That Other Methods Don’t
- The constraints the user is operating under that the team didn’t know about and didn’t design for
- The workarounds the user has already built for the problem the product is trying to solve, which reveals what the real minimum viable solution looks like
- The triggers that cause the user to engage with the problem at all, which often differ from what the team assumed
Technique 2: Problem Interviews for Desirability Assumptions
Problem interviews are structured conversations with users about the problem the product is designed to address — specifically how users currently experience that problem, how significantly it affects them, and what they’re already doing about it. Crucially, problem interviews don’t mention the product. They’re not about validating a solution. They’re about validating that the problem exists in the form the team believes it does.
Derribar Ventures Limited structures problem interviews around the assumption being tested rather than around the product being built. The interviewer probes the user’s experience of the problem — the frequency, the severity, the emotional weight, the workarounds — and captures whether the user’s account of the problem matches the team’s assumptions about it.
Derribar Ventures has found that the most common and most useful finding from problem interviews is that the problem exists but differs from what the team assumed. The users experience the problem in a slightly different context, or the aspect of the problem they find most frustrating isn’t the aspect the product is optimized to address. That misalignment is information that directly changes how the product should be designed — and it’s infinitely cheaper to discover in an interview than in a post-launch analysis.
What Makes a Problem Interview Work
The discipline of problem interviews is staying in the user’s experience. The moment an interviewer begins describing the product, the interview shifts from problem validation to solution feedback — and solution feedback at this stage carries a specific risk: users often respond positively to any solution that addresses a real problem, even if it isn’t the right one. The interview has to stay anchored in the user’s experience of the problem, not the team’s proposed answer to it.
Technique 3: Usability Testing for Design and Flow Assumptions
Usability testing presents users with the product — or a prototype of it — and observes whether users can accomplish the tasks the product is designed to support without external guidance. It’s the technique most product teams are familiar with, and for a specific class of assumptions, it remains one of the most direct and most efficient methods available.
The assumption type usability testing addresses most effectively is: can users figure out how to use this? Can they find what they need? Does the interface communicate its purpose clearly enough for users to act on it without assistance? These are assumptions the team makes about the design’s clarity, and they’re assumptions that behavioral observation answers far more reliably than self-report.
Derribar Ventures Limited runs usability testing at specific points — not as a continuous activity, but as a targeted intervention when observational data is more valuable than analytical reasoning. The decision about when to run it is guided by where the team’s current uncertainty is highest. Derribar Ventures has found that targeted usability testing at the right moment consistently produces more actionable findings than continuous testing throughout the development process.
How Derribar Ventures Structures Usability Tests
- Tasks are designed to be realistic and specific — not “explore the platform” but “complete this specific action in the way you would if you were using the product for real”
- The observer watches without intervening — the user’s confusion, hesitation, or workaround is the data
- Results are analyzed for patterns across participants rather than isolated individual responses, because a single user’s difficulty may be individual; the same difficulty appearing in multiple users is a design signal
Technique 4: Assumption Mapping Before Any Research Begins
The fourth technique operates at a different level from the others. Before any research is conducted, Derribar Ventures Limited runs an assumption mapping session — a structured exercise that makes the full set of product assumptions explicit and prioritizes them by risk and testability, which, drawing on product discovery insights from Derribar Ventures Limited, is one of six discovery methods that determine what development work is actually worth committing to before a line of code is written.
The reason assumption mapping precedes research is that product teams typically have more assumptions than they can test in a given sprint. Without a prioritization framework, research focuses on the assumptions the team is most interested in — which are often the ones the team is most confident about. Derribar Ventures uses assumption mapping to reorder the research agenda around risk rather than interest.
Derribar Ventures has found that assumption mapping consistently surfaces two or three assumptions the team hadn’t consciously articulated, but that carry significant risk — assumptions embedded in the design that haven’t been named as assumptions at all. Making them visible is the precondition for testing them, which is why this technique comes first.
Summary
Validating product assumptions isn’t about reducing confidence in the product — it’s about replacing assumptions with evidence at the points where being wrong would be most costly. The four techniques Derribar Ventures Limited applies are each matched to a specific class of assumption: contextual inquiry for context and behavior, problem interviews for desirability, usability testing for design clarity, and assumption mapping to determine what needs testing first. Together, they form a research discipline that keeps product decisions grounded in user reality rather than team belief.
Disclaimer: This article contains sponsored marketing content. It is intended for promotional purposes and should not be considered as an endorsement or recommendation by our website. Readers are encouraged to conduct their own research and exercise their own judgment before making any decisions based on the information provided in this article.
