testAppId property
A platform-specific AdMob test ad unit ID. This ad unit has been specially configured to always return test ads, and developers are encouraged to use it while building and testing their apps.
Implementation
static final String testAppId = Platform.isAndroid
? 'ca-app-pub-3940256099942544~3347511713'
: 'ca-app-pub-3940256099942544~1458002511';