How to run one-time setup code before executing any XCTest

Question

I have the following problem. I want to execute a piece of code before all test classes are executed. For instance: I don't want my game to use the SoundEngine singleton during executing, but the SilentSoundEngine. I would like to activate the SilentSoundEngine one time not in all tests. All my tests look like this:

class TestBasketExcercise : XCTestCase {        
    override func setUp() {
        SilentSoundEngine.activate () // SoundEngine is a singleton
    }
    // The tests 
}

-Edit- Most of the answers are directed at providing custom superclass for the TestCase. I am looking for a more general and cleaner way to provide the environment that all tests need to execute. Isn't there a "main" function/ Appdelegate like feature somewhere for tests?

Answer 1

From Writing Test Classes and Methods:

You can optionally add customized methods for class setup (+ (void)setUp) and teardown (+ (void)tearDown) as well, which run before and after all of the test methods in the class.

In Swift that would be class methods:

override class func setUp() {
    super.setUp()
    // Called once before all tests are run
}

override class func tearDown() {
    // Called once after all tests are run
    super.tearDown()
}