Stress-testing desirability, viability, and feasibility before you build
One of our mentors, Harry, ran a stress-testing workshop at the NHS Clinical Entrepreneur Programme Pitstop on Saturday.
This week’s Monday Masterclass shares the key principles and a light version of the exercises so you can test your model on paper this week. The aim is simple: prove there is demand, prove the numbers work, and prove you can deliver, before you spend serious time or money.
What stress-testing means in practice
You are checking three things.
- Desirability: are you building something that customers will actually care enough to switch to from their existing alternatives.
- Viability: do the numbers add up for a real business, not just a pilot.
- Feasibility: can you build, sell, and support it with the team and constraints you have.
Your job is to surface assumptions, test the riskiest ones first, and iterate. Common traps include falling in love with your solution, pricing by guesswork, chasing tiny segments, and premature optimisation.
Your working surface: the Lean Canvas
Use a one-page Lean Canvas to capture your current model. Fill it fast. Mark the Leap-of-Faith assumptions that must be true for the model to work. For medtech, note the buyer vs user, early adopters, existing alternatives, and the problem you solve. The canvas is not a pitch. It is a map of what to test next. We’ll be covering more about the lean canvas in other blog posts.
Exercise A: Desirability — do customers care enough to switch?
The goal is to show that real customers with real budget are actively looking for a better way.
- Customer segments and early adopters: write down who pays, then name your early adopters. Identify a switching trigger. What event or pain would make them change now.
- Existing alternatives: list how they solve the job today. Include paper, email, spreadsheets, legacy systems, and workarounds.
- Problems with alternatives: capture the top three pains in their words.
- Value promise: draft one sentence that explains how your way is 3–10x better on what they care about.
Pass signal: you can point to a clear trigger and a believable reason you are much better than the status quo.
Fail signal: vague customers, soft problems, unable to find a way you are better than existing alternatives or a “nice to have”.
Keep this high level. Save interviews, scripts, and scoring for the next steps.
Exercise B: Viability — make the numbers add up
The goal is to check, whether your business model is sustainable on paper, that this is worth building. Here are the key steps:
- Minimum Success Criteria: pick a three-year target that would count as success. Use ARR to the nearest power of ten.
- Average customer size: estimate what one customer will pay per year.
- Scale shape: back-of-the-envelope maths to see how many customers you would need.
- Demand sanity check: sense-check leads and market size using conservative conversion. Ask yourself if your early market is large enough to support the goal.
- If it fails: revisit pricing using value anchors, revisit your segment, or widen the problem you solve.
Keep the maths rough and honest. If it does not work on paper, it will not work in the wild.
Exercise C: Feasibility — can you deliver and grow to your goal?
The goal is to show a believable path from first customer to your MSC.
- Traction roadmap: work back from your three-year goal to year two and year one. Use simple waypoints such as Month 12, Month 24, Month 36.
- Now, Next, Later:
- Now, 3–6 months: reach problem–solution fit. Use demo → sell → build. Seek commitments such as letters of intent, deposits, or paid discovery. Avoid premature optimisation.
- Next, 12–18 months: build and launch the MVP with real early adopters. Use Wizard-of-Oz or Concierge tactics to learn fast. Track traction against the roadmap.
- Later, to month 36: scale sensibly to reach MSC. Team, funding, and expansion fit here.
Keep this about direction, not perfect plans. You are proving a path exists.
After the checks: plan your assumption tests
Once your Lean Canvas passes these three stress tests, list your biggest remaining assumptions. Decide how you will test them. Keep tests small and specific. Focus on evidence over opinions. If you want a primer on good customer conversations, see our review of The Mom Test and sign up to our mailing list to get more articles on designing lean experiments.
A quick worked example
Context: a remote wound care toolkit for community nursing.
- Desirability: early adopters are community teams under pressure to reduce avoidable admissions and travel time. Switching trigger is a new local target on same-day wound reviews. Current alternatives are phone calls, photos on personal devices, and ad-hoc spreadsheets. Top pains are delays, poor image quality, and information governance risk. A simple promise emerges: clearer images, faster triage, safer sharing.
- Viability: MSC is £1 million ARR in three years. Average customer size is £10,000 per organisation per year. You would need roughly 100 paying organisations. Even with conservative conversion, this looks plausible across multiple regions if the value is real.
- Feasibility: Month 12 target is 1 live organisation with paid commitments in two more. Month 24 is 10. Month 36 is 100. Now-phase plan is demo, secure letters of intent, and run a controlled pilot with clear outcome measures such as time to review and admissions avoided.
Outcome of stress testing: proceed, but systematically test your assumptions with interviews and experiments.
Common pitfalls and simple fixes
- Solution-first thinking. Fix: start with existing alternatives and problems with them, not a list of features.
- Tiny segments. Fix: do the viability maths first. If the market is not big enough to support your aspirations think about other customer segments, or finding a bigger problem to solve.
- Premature optimisation. Fix: demo, sell, then build. Commitments before code. Focus on the here and now, don’t dream about the future when you have millions of customers!
What to do next
If you want more practical help like this, join our mailing list, use the form below. Each Monday we share a short masterclass like this packed full of tools techniques and advice.
If you are ready to go deeper, check out our course From Idea to Business Model. We cover the full toolkit behind these exercises, including interview scripts, pricing anchors, benefits calculators, traction worksheets, and medtech-specific checklists for clinical safety and information governance.