Swift and Objective-C

Most of the new projects being created are written in Swift, but larger companies still often support legacy Objective-C frameworks

Testing in the community has gotten better in the last few years, but it's still pretty bad in comparison to other stacks. Some of it is a lack of proper education from Apple, and some of it is poor architecture choices, given that writing tests for MVC is more complicated than in other architecture patterns.

There is still a significant opportunity for Swift/Objective-C developers to embrace unit testing. Those who do will stand out from the crowd.

Apple has made significant improvements to XCTest and Xcode support for testing. I've seen a lot fewer people using alternative frameworks than in past years, as the cost of the learning curve and dealing with support issues usually outweighs the benefits.

UI Tests are much slower to run and often less reliable, they aren't great for TDD workflow, and most companies don't run them on each PR. Instead they are scheduled on CI or nightly builds.

I’m not really surprised to see a slow rate of adoption here since it's still a pretty new stack in comparison to the alternatives. But I spoke to a bunch of engineers working with Swift on Server, and all I heard was praise regarding how well it works.