mokacoding

unit and acceptance testing, automation, productivity

WWDC21: What's New in Testing

As a testing enthusiast, I'm always waiting for a "What's New in Testing" session at WWDC, like the ones from 2017 and 2018. This year I was even keener to learn what was new because of the upcoming launch of my book Test-Driven Development in Swift on July 11th.

Since there was no "What's New in Testing" talk at WWDC21, I thought I'd make one for the WWDC themed Melbourne Cocoaheads Meetup last week. You can see the live stream recording here. I recorded an in-case-of-emergency version beforehand, which I embedded below alongside the slides because it has better video quality. In the same meetup, Jarrod Robins gave a hilarious iOS and macOS new features talk which I recommend too.

Video

Slides

What's New in Testing

The biggest testing news was Apple's new Xcode Cloud service, a Continuous Integration service fully integrated with Xcode and App Store Connect.

Managing CI for Swift apps has historically been tricky because of the hardware constraint that builds need to run on a Mac. There are existing products like Bitrise and TravisCI offer managed solutions, but who better than Apple to provide a managed environment on Apple hardware?

As of this writing, Xcode Cloud is in beta, and I haven't gotten an invite yet, so it's hard to give a concrete opinion. From what we can understand from Apple's demos at WWDC, I think this will be a solid solution for indie developers and small teams that don't have the time or know-how to manage their CI infrastructure.

Another huge announcement, albeit not really a piece of news since Swift development happens in the open, was the introduction of the async/await pattern for asynchronous operations and concurrency. Not only async/await makes writing async code straightforward but also testing it. Check out this post for more details.

XCTest got two new shiny APIs for us to play with. XCTExpectFailure allows you to expect tests to fail. I encourage you to use this API only in extreme cases, like during an extensive rewrite that breaks some code areas. Do not use it to avoid dealing with tests that are broken or flaky. XCTExpectFailure is already available in Xcode 12.5; you don't need to wait for Xcode 13 to use it. You can find the WWDC session here and the docs here.

Another new handy method is addTearDownBlock with which you can push code to execute after a test finishes into a LIFO stack.

A new testing feature coming with Xcode 13 is the addition of a Test Repetition configuration to Test Plans. There are four test repetition modes:

  • None. Do not repeat the tests
  • Until Failure. Runs the tests until one fails, up to three times. Useful to discover flaky tests.
  • Retry on Failure. Will retry the tests that failed up to three times. Helpful to work around flaky tests that you haven't had the time to fix yet.
  • Up Until Maximum Repetition. Will run the tests three times (the number doesn't seem configurable yet) and report the success ratio. Useful to gauge the stability of your test suite.

One feature unrelated to testing that I'm super excited about is Vim key bindings in Xcode. Fun fact, I'm told that Vim keybinding support was requested with Radar 3716281 in July 2004, although I couldn't find a link to that radar.

I've been a Vim user for a long time, and I'm writing this post with Vim. Once you get over the initial learning curve, Vim's modal editing will make you super efficient at manipulating text. It's great to see this powerful text editing capability being added to Xcode.

I'm so excited about Vim key bindings that I'm considering putting together a course about it. Head over here to learn more and register your interest.


WWDC had lots of exciting testing news, and more little nuggets can be found in the Xcode 13 release notes —even though testing is at the very bottom. What was your favorite news? I'd love to hear from you! Leave a comment below or get in touch on Twitter at @mokagio.

And, of course, don't forget to check out Test-Driven Development in Swift if you want to learn more about testing Swift applications.

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