# Validating – Gründerkurse

> Problem interviews, smoke tests, competition: before a line of code is written.

- [How to Validate a Business Idea Before You Build It](https://gruenderkurse.de/en/validating-ideas/validate-business-idea/): To validate a business idea, list the two or three assumptions the business cannot survive without, then test each with real behaviour: interviews about past problems, an offer with a price attached, and a bottom-up market estimate. Decide in advance which result would make you stop, and write it down.
- [Customer Discovery Interview Questions That Work](https://gruenderkurse.de/en/validating-ideas/customer-interview-questions/): Good customer discovery interview questions ask about specific things that already happened: when the problem last occurred, what the person did about it, and what it cost them. Avoid questions about your idea, about future intentions, and anything answerable with yes or no. Close by asking for a small commitment such as an introduction.
- [Smoke Test Landing Page: Measure Demand Before Building](https://gruenderkurse.de/en/validating-ideas/smoke-test-landing-page/): A smoke test landing page presents a product that does not exist yet, with a price and one call to action, and counts how many strangers take a step that costs them something, such as pre-ordering. It only tells you something with a few hundred visitors and a pass mark you set before launch.
- [How to Calculate TAM, SAM and SOM (Bottom-Up)](https://gruenderkurse.de/en/validating-ideas/tam-sam-som/): Calculate TAM bottom-up by multiplying the number of customers who have the problem by the annual price. SAM is the slice your product can actually serve given language, region and features. SOM is the share of SAM you can realistically win within three to five years, checked against how many customers your sales effort can close.

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