Swift2 UI Test - Wait for Element to Appear

Question

I want to have a test pause and wait for an element to appear on screen before proceeding.

I don't see a good way to create an expectation for this and wait using

public func waitForExpectationsWithTimeout(timeout: NSTimeInterval, handler: XCWaitCompletionHandler?)

The method to create an expectation I have been using has been

public func expectationForPredicate(predicate: NSPredicate, evaluatedWithObject object: AnyObject, handler: XCPredicateExpectationHandler?) -> XCTestExpectation

But this takes an already existing element, whereas I would like to have the test wait for an element that does not yet exist.

Does anyone know the best way to do this?

Answer 1

In expectationForPredicate(predicate: evaluatedWithObject: handler:) you don't give an actual object, but a query to find it in the view hierarchy. So, for example, this is a valid test:

let predicate = NSPredicate(format: "exists == 1")
let query = XCUIApplication().buttons["Button"]
expectationForPredicate(predicate, evaluatedWithObject: query, handler: nil)

waitForExpectationsWithTimeout(3, handler: nil)

Check out UI Testing Cheat Sheet and documentation generated from the headers (there is no official documentation at the moment), all by Joe Masilotti.

Answer 2

This question was asked about Swift2 but it's still a top search result in 2019 so I wanted to give an up-to-date answer.

With Xcode 9.0+ things are a bit simpler thanks to waitForExistence:

let app = XCUIApplication()
let myButton = app.buttons["My Button"]
XCTAssertTrue(myButton.waitForExistence(timeout: 10))
sleep(1)
myButton.tap()

WebViews Example:

let app = XCUIApplication()
let webViewsQuery = app.webViews
let myButton = webViewsQuery.staticTexts["My Button"]
XCTAssertTrue(myButton.waitForExistence(timeout: 10))
sleep(1)
myButton.tap()

Answer 3

You can use this, in Swift 3

func wait(element: XCUIElement, duration: TimeInterval) {
  let predicate = NSPredicate(format: "exists == true")
  let _ = expectation(for: predicate, evaluatedWith: element, handler: nil)

  // We use a buffer here to avoid flakiness with Timer on CI
  waitForExpectations(timeout: duration + 0.5)
}

In Xcode 9, iOS 11, you can use the new API waitForExistence

Answer 4

It doesn't take an already existing element. You just need to define the following predicate:

let exists = NSPredicate(format: "exists = 1")

Then just use this predicate in your expectation. Then of course wait on your expectation.