Writing code that is testable, maintainable, usable | Algolia

Writing quality code that is maintainable and extendable is crucial for software companies relying on teamwork or long-term projects. Testability and loose coupling techniques can make code more maintainable, while making it composable and reusable. Integration testing checks parts of the software in isolation with real inputs and I/O systems, while unit testing tests parts of the software in isolation with dummy I/O systems and dependencies. Single Responsibility Principle (SRP) ensures that every part of the software addresses one single concern, making it easier to isolate features for testing. Dependency Injection (DI) is a powerful principle that allows control over dependency initialization outside of the code using them. Mocking dependencies enables complete control over their behavior during tests. Relying on abstract types (interfaces) to mock dependencies throughout the code produces cleaner, less coupled APIs. SRP and DI used in combination produce software with composable features and reusable code. Some dependencies might not be easily mockable due to open APIs or complex 3rd party dependencies, but these issues can be addressed through data access layers and interface segregation principles. Embracing testability design principles also helps make the code more usable in the first place.