This is not really a easy question.
I would try it like this.
1. I ask who will be a kind of standard user. Maybe you can find some specifics way of use or words to search.
2. Define some objects to search.
3. Define the properties. E.g. like in google, the web site which is mostly linked will be the first in the order of results. So you must set your own properties, because it must be able to calculate the result by your self. (e.g.: you search "quality", then you must know this will be the first result, this the second and so on)
4. Test the application with your test words and check the result.
5. Change the properties and calculate the new expected result by your self (this time maybe will be the first page of the first result the last one in this result)
But i think, it will be effectively to test such an complex allgorythim in an automated unit test. I would test in the Blackboxtest only the integration of the moduls, the performance and maybe the display of the result
Darrel is once again the leader in simplification. I totally agree, (on this one subject), that he has given the easiest method. Unless there is more to the context than has been described in the question.
Success is the ability to go from one failure to another with no loss of enthusiasm.
~ Winston Churchill ~