# Test Before You Build

**Summary:** Customer validation through 20 interviews with realistic potential customers, followed by a clear BUILD, CHANGE, or KILL recommendation.

**Service provider:** Dr. Kari Jääskeläinen
**Last updated:** 16 September 2026
**Canonical HTML:** https://testbeforeyoubuild.com/

## Find out if customers actually want your idea before you build it

We find 20 potential customers, interview them, analyse what they tell us, and give you a clear recommendation: **BUILD, CHANGE, OR KILL**.

The service is designed for B2B and B2C products, services, software, and research-based innovations where realistic potential customers can be identified.

## How it works

1. **You tell us your idea.** You explain the product, target customer, and assumptions you want to test.
2. **We find the right people.** We identify 20 realistic potential customers in the target market.
3. **We interview them.** We discuss the problem, current alternatives, buying behaviour, and willingness to pay.
4. **We analyse the evidence.** We identify repeated patterns, objections, demand signals, and important changes.
5. **You make the decision.** You receive a BUILD, CHANGE, or KILL recommendation.

## What the validation tests

- Problem severity
- Current customer behaviour
- Willingness to change
- Willingness-to-pay signals

## Who it is for

The service is a strong fit when you can identify potential buyers, face a meaningful investment decision, and are willing to change or stop the idea if the evidence points that way.

It is not a substitute for statistically representative market research, and it is not intended to produce positive feedback for a decision that has already been made.

## Idea Validation Sprint

The fixed project price is **€2,900 + VAT**. It includes target customer definition, 20 interviews, demand validation, buying objections, customer language, willingness-to-pay signals, key findings, recommended changes, and a BUILD / CHANGE / KILL conclusion.

[View full market validation service details and pricing](https://testbeforeyoubuild.com/market-validation-services-pricing/).

## About Dr. Kari Jääskeläinen

Dr. Kari Jääskeläinen is an entrepreneur, business leader and consultant whose work combines market validation, technology commercialization and practical business development.

He has completed around 200 commercialization and business development projects and co-founded ventures in MedTech, private higher education, wireless technology and artificial intelligence.

[Read about Dr. Kari’s experience](https://testbeforeyoubuild.com/about-kari-jaaskelainen/).

## Customer interview sample size

There is no universal interview number for every validation project. The right scope depends on participant relevance, the segments that must be understood, the evidence added by each interview and the decision the research must support.

[Read how many customer interviews are enough](https://testbeforeyoubuild.com/how-many-customer-interviews/).

[Read how to validate a business idea before you build](https://testbeforeyoubuild.com/how-to-validate-a-business-idea/).

[Read about the market validation process, methods and examples](https://testbeforeyoubuild.com/market-validation/).

[Read the B2B customer research and participant recruitment guide](https://testbeforeyoubuild.com/b2b-customer-research/).

[Read the customer discovery interviews guide](https://testbeforeyoubuild.com/customer-discovery-interviews/).

[Read how to validate a SaaS idea before building an MVP](https://testbeforeyoubuild.com/how-to-validate-a-saas-idea/).

[Read how to test willingness to pay before you build](https://testbeforeyoubuild.com/how-to-test-willingness-to-pay/).

[Read how to validate a customer problem before designing the solution](https://testbeforeyoubuild.com/how-to-validate-a-customer-problem/).

[Read about customer interview bias, leading questions and other mistakes](https://testbeforeyoubuild.com/customer-interview-bias/).

## Frequently asked questions

### What kinds of ideas can you test?

We focus mainly on B2B or B2C products, services, software, and research-based innovations where realistic potential customers can be clearly identified.

### Is the service limited to 20 interviews?

No. The standard €2,900 + VAT service includes 20 interviews. Projects involving multiple customer segments, buyer roles, countries, use cases or broader objectives can be scoped and priced separately.

### Do you only interview people who already know us?

No. The goal is to speak with realistic potential customers, not only people already connected to your organisation.

### What do we receive?

You receive a report containing the main findings, demand signals, objections, recommended changes, and a clear BUILD, CHANGE, or KILL recommendation.

## Contact

[Submit your idea on the website](https://testbeforeyoubuild.com/#contact).

## Sources

This page describes the Test Before You Build service and the professional experience supplied by its service provider. It makes no claim that 20 qualitative interviews produce statistically representative evidence.