Use Proper Tests LifeCycle

[michalsrutek]

Use Proper Tests LifeCycle

XCTestCase works differently from a standard Swift class. It uses Objective-C runtime in the background.

That is why there should never be stored properties created directly inside of the class.

The reason being, that with having

final class PhoneNumberTextFieldTests: XCTestCase {
    private let phoneNumberKit = PhoneNumberKit()
    ...
}

the test case lifecycle for n tests would look like this

• init phoneNumberKit-1
• init phoneNumberKit-2
• ...
• init phoneNumberKit-n
• run test-1
• run test-2
• ...
• run test-n

(Note that the phoneNumberKit-s never get deinitialized! ⚠️ )

There are (at least) 2 ways to solve this

1. Create phoneNumberKit at the start of each test (this adds visual noise)
2. Define phoneNumberKit as an unwrapped optional and use setUp() to initialize it and tearDown() to clear it

I would suggest we go with the second approach.

That way, we would have

• init phoneNumberKit-1
• run test-1
• deinit phoneNumberKit-1 ✅ // deinit was not called before (at all!)
• init phoneNumberKit-2 ✅ // all the init-s were run before the tests
• run test-2
• deinit phoneNumberKit-2
• ...

Source: iOS Unit Testing by Example by Jon Reid or his website (or better yet - you can try it yourself!)

[bguidolim]

Thanks for this refactoring :)