I did not understand the nature of XCUICoordinate and what I was doing with SwiftUI Canvas. Let p1 be a known point in my drawing, and p2 be the canvas midpoint. I generated coordinate objects for the points. I used p1Coordinate.press(forDuration: 2.0, thenDragTo: p2Coordinate, ... followed by p2.click(). I replaced the use of p2 with p1.click() and the test worked. Thank-you for your help.