This whole discussion has been about an "interface refactoring". I.e. a change to internal interfaces so obviously anything that sees that interface is subject

This whole discussion has been about an "interface refactoring". I.e. a change to internal interfaces so obviously anything that sees that interface is subject to change. Now it is true that some interfaces are more stable than others, and you can make a good argument that testing shouldn't be done at boundaries that are likely to be unstable.