How to assert if a view is off screen

UITest.swift

import XCTest

class UITests: XCTestCase {
    let app = XCUIApplication()

    override func setUp() {
        super.setUp()
        continueAfterFailure = false
        app.launch()
    }

    func testElementIsOnScreen() {
        let windowFrame = app.windows.elementBoundByIndex(0).frame
        let onScreenElementFrame = app.buttons["On"].frame
        let offScreenElementFrame = app.buttons["Off"].frame

        XCTAssert(CGRectContainsRect(windowFrame, onScreenElementFrame))
        XCTAssertFalse(CGRectContainsRect(windowFrame, offScreenElementFrame))
    }
}