Use Cases and Deployment Scope
Im a Fullstack Mobile developer, I usually make Android apps, but I have experience with Swift, Objective-C, and iOS; XCTest has been really useful for Unit Testing for those platforms and languages. Before the use of XCTest, we had a lot of issues when we changed or made refactors on the code, and we needed to stop to fix all of those issues, but since we added XCTest, we don't need to worry about that, because XCTest will tell us what was broken.