How to let the app know if it's running Unit tests in a pure Swift project?

Question

One annoying thing when running tests in Xcode 6.1 is that the entire app has to run and launch its storyboard and root view controller. In my app this runs some server calls that fetches API data. However, I don't want the app to do this when running its tests.

With preprocessor macros gone, what's the best for my project to be aware that it was launched running tests and not an ordinary launch? I run them normally with command + U and on a bot.

Pseudocode:

// Appdelegate.swift
if runningTests() {
   return
} else {
   // do ordinary api calls
}

Answer 1

Elvind's answer isn't bad if you want to have what used to be called pure "Logic Tests". If you'd still like to run your containing host application yet conditionally execute or not execute code depending on whether tests are run, you can use the following to detect if a test bundle has been injected:

if NSProcessInfo.processInfo().environment["XCTestConfigurationFilePath"] != nil {
     // Code only executes when tests are running
}

I used a conditional compilation flag as described in this answer so that the runtime cost is only incurred in debug builds:

#if DEBUG
    if NSProcessInfo.processInfo().environment["XCTestConfigurationFilePath"] != nil {
        // Code only executes when tests are running
    }
#endif

Edit Swift 3.0

if ProcessInfo.processInfo.environment["XCTestConfigurationFilePath"] != nil {
    // Code only executes when tests are running
}