Xcode unit testing

Question

I have never used Unit Testing and I understand the uses of it but I don\'t really know when and how to use it.

I would like to know when it\'s worth it to use Unit

Answer 1

You should almost always unit test and you should write code with unit tests in mind. The extremists write tests even before writing the code (it's called TDD - Test Driven Development).

I'll give you a real life example: I recently had to code a sorted NSArray that supports "intervals". Meaning, the array should know how to insert an interval and keep it sorted.

For example, the array would look like this: [1-3, 5-9, 12-50]. In this example there are 3 intervals in the array, and as you can see they are sorted. After I wrote my class (I called it IntervalsArray), I HAD to write tests to make sure that it works correctly and that I will not "break" it if I or someone else make changes to the code in the future.

Here are some example tests (pseudo-code):

Test 1:

- Create a new IntervalsArray
- Insert a new interval to the array
- (TEST) make sure the array has 1 object in it

Test 2:

- Create a new IntervalsArray
- Insert 2 intervals into the array: [1-3] and [5-9]
- (TEST) make sure there are 2 items in the array
- (TEST) make sure interval [1-3] comes before interval [5-9]

At the end I had something like 15 tests to cover every aspect of my new array.

Here's a good unit-testing with Xcode tutorial.

You can also write logic tests (which are more complicated than unit tests) to test your UI. Read a little about UIAutomation, which is Apple's way of testing UI. It's not perfect, but it's pretty good. Here's an excellent tutorial about this.

If you consider yourself a good programmer, you should write unit-tests for your code.