i wish i could give you 1 thousand points. isolated unit tests can have value in that the bugs they expose are more easily tracked down. full-system testing, w

i wish i could give you 1 thousand points. isolated unit tests can have value in that the bugs they expose are more easily tracked down. full-system testing, with an honest attempt to do fault injection, by definition exposes all the issues you might have in production. if you have a decent test suite you can honestly claim you can expect it to take client code correctly. i don't know how thats true if you've only tested A against some stubbed out version of B that always returns success. integrated testing is harder and requires more framework. its also kinda necessary, and if you only have the resources to do one or the other, the choice seems pretty clear. i also heartily agree with your comment that since we're supposed to have frictionless and scalable deployment. there is no reason not to test this as part of integration testing and also exploit this function to make integration testing easier.