While doing any application your code must be tested-one and in iOS, Unit testing is preferred for that part. But why we need Unit testing? What are the reasons to use unit testing? Unit testing is the program that automatically checks the result of your application to avoid further errors.
Unit Testing allows us to prevent the most important Run-time error. The runtime error is basically not an error when you code like missing semicolon or wrongly typing the method name etc. That time compiler prompts you that there is a problem and you need to fix this because it is a syntactical error. But the run time error comes into the picture when you build your app and the app crashes when the user uses it. At that time, you may not understand why the app crashed. So to prevent this type of run time error, you need unit testing. Unit testing also prevents the Logical error, like when your app is asking the permissions to access the user contact information if the user gives permission then it’s ok. But if he dines the permission that time also unit testing is needed.
When you create a project, that time it is added to your project automatically. You just need to write a different case to avoid the above errors.