Detect if the app was launched in the iOS Simulator to execute the unit tests. Source: http://www.objc.io/issue-1/testing-view-controllers.html

isRunningTests.c

static BOOL isRunningTests(void) {
    NSDictionary *environment = [[NSProcessInfo processInfo] environment];
    NSString *injectBundle = environment[@"XCInjectBundle"];
    return [[injectBundle pathExtension] isEqualToString:@"octest"];
}

This fails if it is running xctest.

Well, replace @"octest" by @"xctest and rulez