Add tests for the API

[j-f1]

Presently, there are no automated tests for the API beyond making sure it builds successfully. We should have some tests that spin up a server, run through some/all of the supported ops, and check a few error cases. This would make it less likely that unrelated changes would accidentally break the API.

[twk3]

with #1991 and #2036 about half the current API functions are covered

should be short work to finish the rest

[MatissJanis]

@twk3 I believe we can now close this issue. Can you confirm?

[twk3]

Yes let's close it. There are a few less common handlers like runQuery that aren't covered. But all the ones that represent entities are now in place.