Add test to ensure interface does not change

[GitHK]

Ensure the content of NodeGetIdle | NodeGetUnknown | DynamicServiceGet | NodeGet does not change in a breaking way. We need a test for these.

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          if this code is shared by different services, that is good.

But now, if I change NodeGetUnknown for some reason. where will I see that this function now fails? that is what I mean. And in this case, I guess you might be better served by a common interface than having 4 different objects. but that is just a thought.

Originally posted by @sanderegg in #5892 (comment)