Cast from XCUIElement to unrelated type '[AnyObject]' always fails while fetching JSON

before

if let careProviders = providerJSON["care_providers"] as? [AnyObject]

after

if let careProviders = providerJSON["care_providers" as NSString] as? [AnyObject]

参考：

http://stackoverflow.com/questions/32715160/xcode-7-strange-cast-error-that-refers-to-xcuielement