iOS: index from tableView in Unit Test

I have a question about Unit Test. In one of my test I have something like that:

let obj = array.findElementFromIndex(index)
XCAssertNotNil(obj)

I want to check if my obj is not nil, but the index is from the row of tableView that I select. So in the Unit Test how can I take the information about the index of row that i selected to check if the object is or not null?

Thanks