That's an arbitrary division of "one thing" though. You've decided the "one thing" includes the HTTP request and response, but it doesn't involve the socket cal

That's an arbitrary division of "one thing" though. You've decided the "one thing" includes the HTTP request and response, but it doesn't involve the socket call for that request and response. I'm not saying the test has to involve a network, or a network card, or anything like that, but perhaps a more accurate reflection of the "unit" to be tested is something that reads and writes to a channel or even a socket (and again, not necessarily a TCP/IP socket). In reality, you're actually testing a bunch of method invocations that won't happen when the code is being used, and to do it, you're also breaking a lot of the contracts that one would otherwise expect to be maintained... maybe that's not the optimal way to do things.