UI Testing with respect to a attribute value iOS/Swift

I'm writing UI Tests for my application. I've an attribute named numberOfPhotos in PhotosViewController and it's value is set from another ViewController. Whenever numberOfPhotos is 2, only two photos should be displayed in my current PhotosViewController.

I was able to test if required number of images are visible or not but I'm not able to set numberOfPhotos from UITests class. Is there anyway I can set this value and proceed to tests.

Currents I'm editing the code to set value for numberOfPhotos and testing it. Is there anyway I can set this value from UITests class. Thanks.