Q:

End to end testing of write-only apis

In our deployment process for our services, besides unit and integration tests, we also have a little smoke test for our services.  Mostly for verifying that the deployment went well, cloud services set up correctly with working connection strings and working domains. 
For most services this is quite easy.  Make a request to a endpoint you know would hit the db and check the response.  
We now have a write only service where fat clients write some data for verification and logging because they are billed for their activities later. 
Is there a good way for us to write smoke tests for this kind of service.  I'm seeing a analogy to credit cards where I know there exists special test cards which doesn't charge any data.  So In our service we could hard code some test guids that won't commit a transaction or something like that. 
Is there a better approach? 

A:

If the goal of your smoke test is to check that a fat-client can call some function in your write-only-service to make shure that network connectivity is ok and the service is running why not add an extra non-read-only service method called "self-test" that replies something defined to the fat-client and that would not be charged. 
it could be something similar to the network "ping"-command

