Testing AdMob integration

I have a quick question about integrating AdMob into your app (in my case with Unity).

The tutorial said to use the following lines during testing:

return new AdRequest.Builder()
            .AddTestDevice(AdRequest.TestDeviceSimulator)
            .AddTestDevice("deviceID")
            .Build();

Is this supposed to show dummy ads (like UnityAds does), or real ads but give no reveue? When testing on my phone I am getting real ads I can click on and direct me to a valid app on the store. However, on the AdMob dashboard I don't get any revenue or impressions.

I just want to make sure this is correct, and I won't get into any legal trouble by faking impressions. Thanks!