The initial thought here is to introduce a MethodTestCase type that
encapsulates the behavior of testing a single method in a particular given
service.
To do so, a httptest.Server is created and the schema is turned into a request
which is fired at that server. Thet MethodTestCase, of course, knows how to
respond to different requests, and the behavior of those responses is tested.
What I dislike is that we have to write three things which are mostly the same
to test any endpoint in any case on the API:
1) a request type (Go struct)
2) an expected response type (Go type)
3) the actual response (a mutltline Go string, which is really just JSON)
This seems redundant, so I may explore other options for implementing this sort
of thing in the future.
