[marcosdumay]

You have to:

1. Have an overall idea of what your software will do before writing the first line of code.

2. Challenge and change any touched assumption from #1 during development when you refine that idea.

3. Test that the program satisfies your refined idea after it's written.

4. Create some assurance you'll keep #3 correct while you write any further code later.

However you fulfill those needs, if you got them all, you are good.