Please note that Unity IAP is not compatible with the IL2CPP scripting backend which is currently experimental on Universal Windows Platform.
Unity IAP features support for Microsoft’s In App Purchase simulator which allows you to test IAP purchase flows on device before publishing your application.
The simulator can be enabled when configuring Unity IAP before initialization, as follows:
var builder = ConfigurationBuilder.Instance(StandardPurchasingModule.Instance());
builder.Configure<IMicrosoftConfiguration>().useMockBillingSystem = true;
Be sure to disable the mock billing system before publishing your application.