 
         let expectation3 = expectationWithDescription("background image should download successfully")
         var highlightedStateImageDownloadComplete = false
-        URL = NSURL(string: "https://httpbin.org/image/jpeg?random=\(randomInt())")!
+        URL = NSURL(string: "https://httpbin.org/image/jpeg?random=\(arc4random())")!
 
         button.af_setImageForState(.Highlighted, URL: URL)
         button.imageObserver = {


        let expectation4 = expectationWithDescription("background image should download successfully")
        var disabledStateImageDownloadComplete = false
        URL = NSURL(string: "https://httpbin.org/image/jpeg?random=\(randomInt())")!

        button.af_setImageForState(.Disabled, URL: URL)
        button.imageObserver = {

        waitForExpectationsWithTimeout(timeout, handler: nil)
        let expectation2 = expectationWithDescription("background image should download successfully")
        var selectedStateBackgroundImageDownloadComplete = false
        URL = NSURL(string: "https://httpbin.org/image/jpeg?random=\(arc4random())")!

        button.af_setBackgroundImageForState(.Selected, URL: URL)
        button.imageObserver = {
