Xcode UI Testing Getting Background of Cell

I have trouble in using Xcode UI testing to detect if the background of the cell changed.

So, I have a collection view with many cells. Every time I tap a cell, the background of the cell will be changed by setting backgroundView property of the cell.

I have tried updating accessibilityLabel everytime I tap a cell to detect background changes but in the UI testing, the element value of that cell doesn't change.

How can I do detect the background changes? Thanks!