That's the purpose of clear, concise, and complete project requirements; to make sure you get where you want to go.

Comprehensive requirements are both a lamp to guide you down your development journey and guideposts to ensure you stay on the right path.

Plus, they practically write your test cases for you.

If you don't wind up where you wanted to go, maybe you had the wrong map. And, in these parts, that can get you way off course.