It accepts XCUICoordinate in my tests in Xcode 9.2
extension XCUICoordinate {
open func press(forDuration duration: TimeInterval, thenDragTo otherCoordinate: XCUICoordinate)
}
I can use it as follows:
let fromCoordinate = contentElement.coordinate(withNormalizedOffset: CGVector(dx: 0.5, dy: 0.5))
let toCoordinate = fromCoordinate.withOffset(CGVector(dx: 0, dy: 260))
fromCoordinate.press(forDuration: 0.01, thenDragTo: toCoordinate)