Appendix A: Writing Testable Code

The Xcode integrated support for testing makes it possible for you to write tests to support your development efforts in a variety of ways. You can use tests to detect potential regressions in your code, to spot the expected successes and failures, and to validate the behavior of your app. Testing improves the stability of your code by ensuring that objects behave in the expected ways.

Of course, the level of stability you achieve through testing depends on the quality of the tests you write. Likewise, the ease of writing good tests depends on your approach to writing code. Writing code that is designed for testing helps ensure that you write good tests. Read the following guidelines to ensure that your code is testable and to ease the process of writing good tests.