To get test ads on this device, call: request.testDevices = [NSArray arrayWithObjects:GAD_SIMULATOR_ID, nil];

You have to add your test devices. With Swift, just replace

bannerView.load(GADRequest())

with

let request: GADRequest = GADRequest()
request.testDevices = [kGADSimulatorID]
bannerView.load(request)

If you have an iPhone, then run the application too and it will tell you the ID.

To get test ads on this device, call: request.testDevices = @[@"HERE IS THE ID"];

ID added:

let request: GADRequest = GADRequest()
request.testDevices = ["PUT HERE THE ID", kGADSimulatorID]
bannerView.load(request)

At finally fix the bug friends..

I made mistake to generate adUnitID. So only i cannot get ad view.

Now get one adUnitID from xxxx site for testing. And its working fine..

adUnitID = @"a14dccd0fb24d45";

Thanks for All Supporters.

Since the newest update the request.testDevices has been replaced with:

GADMobileAds.sharedInstance().requestConfiguration.testDeviceIdentifiers

I have gotten it to work with this:

GADMobileAds.sharedInstance().requestConfiguration.testDeviceIdentifiers = [(kGADSimulatorID as! String)]

[EDIT]

In my app delegate I am using this code:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
    // use this for production 
    GADMobileAds.sharedInstance().start(completionHandler: nil)
    // use this for testing 
    GADMobileAds.sharedInstance.requestConfiguration.testDeviceIdentifiers = [ kGADSimulatorID ]
        
    return true
}

This is for Swift 5, iOS 13 and Google-Mobile-Ads-SDK (7.58.0)