to prevent accidental clicks during (debug mode) development I use it like this
(placed at the top in the variables so that I don't need to touch the rest of the class source when using it in another project)
B4X:
#if debug
Dim admobInterstitialID As String="ca-app-pub-3940256099942544/1033173712" 'test ID
#else
Dim admobInterstitialID As String="ca-app-pub-.../..." 'your interstitial placement id
#end if