Writing an ebook first can make the project too large. You plan chapters, write drafts, design a cover, and sometimes lose sight of the specific problem buyers wanted solved.
A smaller product is often better for the first test: a margin sheet, product comparison table, Shorts planning board, or blog editing checklist. These are easier to make and the result is clearer for the buyer.
If no one cares, you did not spend weeks writing a book. If people respond, then expand the material with explanations and examples.