How to test touching specific coordinates in my custom calendar view

I developed a custom view which shows a matrix of rectangles representing days and times. When the view is touched within a specific rectangle the view reports the day and time associated with the rectangle. I would like to test this behaviour. But I cannot find how to have the android system (espresso) touch the screen at specific coordinates.

How can I instruct espresso (or any other instrumentations test system) to touch the screen at specific coordinates?