Add XCTWaiter ?

[eonist]

// function to wait for an ui element to appear on screen, with a default wait time of 20 seconds
// XCTWaiter was introduced after Xcode 8.3, which is handling better the timewait, it's not failing the test.  It uses an enum which returns: 'Waiters can be used with or without a delegate to respond to events such as completion, timeout, or invalid  expectation fulfilment.'
@discardableResult
func uiElementExists(for element: XCUIElement, timeout: TimeInterval = 20) -> Bool {
    let expectation = XCTNSPredicateExpectation(predicate: NSPredicate(format: "exists == true"), object: element)
    let result = XCTWaiter().wait(for: [expectation], timeout: timeout)
    guard result == .completed else {
        return false
    }
    return true
}

[eonist]

ref https://stackoverflow.com/a/52898914/5389500