In the last project I must modified the search results.
To verfiy the functionality, I reprovisioning the webs and the demo content every time when I was ready. I removed the webapplication to, because I simluated a new provisioning of the application.
But I figured out that I got after each install and fullcrawl the fresh data. After a little research I figured out that I got an old index in the searchstore.
I did an index reset in the central administration.
The other way is that I do the crawl minimum three times to get the correct result. This is time consuming and an index reset with an fullcrawl was the best way.