Starting on a mobile app can be a daunting proposition.
Your stakeholders at Rex’s Gym really need this app to help drive customer retention, promote the business, and make payments a breeze.
Getting the development environment set up, learning a new language, understanding a wholly different API for screen layouts per-platform, having to go to the Apple Store and buy a Mac (which is the absolutely last thing you thought you would ever do).
Dependency injection (DI) is a design pattern meant to transform hard-coded dependencies into swappable ones, generally at run-time. DI is the primary mechanism by which to implement Inversion of Control (IoC) techniques to load dependencies at run-time as well as the most effortless way to swap dependency implementations with mocks or stubs for unit testing. DI is a best practice that yields more readable and maintainable code due to the way all of an implementation’s dependencies are knowable at-a-glance and by the amazing side effect of creating easily testable code.
Having a suite of automated tests for your code helps improve software quality and maintainability in several dimensions. Writing unit tests for your software is likely to cause you to incorporate several design aspects that make it easier for other developers to use your and which have the side-effect of dramatically increasing the maintainability of your code overall. Testable code typically has fewer tight couplings between components, dependencies that are injectable, and encourages SOLID design principles in a naturalistic way because SOLID code makes writing tests (and therefor all usage) of your code easier. Automated unit tests also help you write a verifiable usage contract between your components that enables you to find and isolate bugs or perform major refactoring on your code without fear of breaking existing features. All of this leads to higher quality software.