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UI Testing in Swift

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To round out my blog series on an introduction to Swift, this posting will be covering UI Testing. Previously we created a simple Swift program to draw a Koch Snowflake, adding some unit tests and then added some performance tests.

The source code for the project is on Google Drive here.

UI Testing actually runs the program like an end user would run the program and if you switch to the simulator while the test is running you can watch these actions take place. Unlike many other UI testing frameworks, this one just interacts with the screen controls, if done properly there is no code involving doing things at specific (x,y) co-ordinates. The magic that makes this work is the iOS accessibility layer that was created to help people with disabilities use Apple products. For instance, the VoiceOver feature that reads the screen needs to interact with the controls in the same way as our UI Tests.

This then means that UI Tests also provide a good means for testing some of the accessibility aspects of our iOS applications. Fully supporting accessibility is an often neglected area and really deserves more consideration. The great thing here is that by making your UI Tests thorough you are also validating that many accessibility technologies will also work.

UI Testing in XCode

When you create a new Swift project in XCode and select unit testing you also get a skeletal group for UI Tests with some setup and a dummy test. You create you test by selecting an empty (or not) test and then pressing record and then manually perform the tests. When you close the simulator a bunch of recorded code will be pasted into your project. This then is a great starting point for writing more thorough tests. You then use all the same XCTAssert type functions as in the unit testing framework to check for problems.

Screen Shot 2016-06-15 at 8.41.45 AM


Not Having Accessibility Setup Correctly

If you haven’t set an accessibility identifier for your control, you won’t get the correct code recorded. Recording will try its best, but it will give you something that probably won’t work. This happened to me. I kept the bad code from the first attempt in the file commented out so you can see it. Generally, if the accessibility is setup right, the code is simple complete and will work. If not, you will find things you did not recorded and other things having hardware or synchronicity problems (strange errors which if you google have workarounds but it all becomes quite complicated).

Screen Shot 2016-06-15 at 8.42.06 AM

Keyboards and other Hardware

I performed my tests on my MacBook which of course has a fixed keyboard. When recording tests, make sure you use the iOS keyboard (that is on the screen). Generally, you want the tests to use all the iOS stuff and not the macOS stuff which makes using the simulator easier. Another approach is to access text fields via the clipboard using cut/paste so as to avoid the keyboard entirely. I tend to think for a good UI test you should test all the cases, but perhaps not on every text field. Also beware text already in text boxes that may need to be cleared first. One way to do this (probably the best way) is to add a clear button in the text boxes properties and then press this. In the recorded sample I hit the delete key a couple of times. Note that tapping a field usually doesn’t select all the text.


Beware that if you cause something to popup or be created, chances are your test code will run faster than that and start using things before they are created. You will need to add wait loops to wait for controls to exist before using them. This case doesn’t happen in the Koch snowflake program. Generally, you don’t want to insert sleep type statements to wait a couple of seconds, this slows down your UI tests and can prove unreliable and lead to investigating a lot of false failed tests. Always better to look for specific events and to proceed quickly.

The Test

The code for the test is below. The setUp and teardown methods were generated by XCode and I didn’t change them. The code for the testExample routine was generated by recording, then I just cleaned up a bit of noise. The intent is that it sets fractal level to 3 and then to 4. If you click on the simulator while running, then you can see this happen. Unfortunately, there isn’t really a good way to validate that it works correctly, so this is really only a run without crashing sort of test, unless you manually observe it.

//  KochSnowFlakeUITests.swift
//  KochSnowFlakeUITests
//  Created by Stephen Smith on 2016-05-13.
//  Copyright © 2016 Stephen Smith. All rights reserved.

import XCTest

class KochSnowFlakeUITests: XCTestCase {

    override func setUp() {

        // Put setup code here. This method is called before the invocation of each
        // test method in the class.
        // In UI tests it is usually best to stop immediately when a failure occurs.

        continueAfterFailure = false

        // UI tests must launch the application that they test.
        //Doing this in setup will make sure it happens for each test method.

        // In UI tests it’s important to set the initial state -
        // such as interface orientation - required for your tests before they run.
        // The setUp method is a good place to do this.

    override func tearDown() {
        // Put teardown code here. This method is called after the invocation of
        // each test method in the class.

    func testExample() {

        let app = XCUIApplication()

        let deleteKey = app.keys["delete"]

        let returnButton = app.buttons["Return"]



The UI testing support built into XCode and Swift is quite nice. Certainly comparable to some quite expensive packages available in the Windows world. Since iOS and macOS are quite a controlled environment and the accessibility support is quite good, this makes this package quite nice. The main thing to watch out for is the proliferation of Apple hardware to check. It appears that going forwards Apple is spending quite a bit of time ensuring automated testing works quite well for their development platform.

Written by smist08

June 15, 2016 at 4:09 pm

Posted in Mobility, programming

Tagged with , , ,