Test 1: The $1 landing page
One headline, one promise, one email field. Spend $50 on targeted ads. If you can't get a 5% signup rate from cold traffic that already has the problem, the problem isn't sharp enough yet.
Test 2: The pre-sale
Offer the thing for half price to the first 10 buyers. Stripe link, no product yet. If five strangers pay, you have a business. If zero do, you have a hobby — better to find out now.
Test 3: The walk-through
Sketch the core flow in Figma. Sit with five people in your target market and watch them try to explain what each screen does. If they can't, the value prop is wrong, not the design.
What doesn't count as validation
Friends saying 'cool idea'. LinkedIn likes. Survey results from people who'll never pay. Validation means money or signed intent — anything else is theatre.