I must first correct, this is not a BUG. This is a feature that we have not implemented yet.
Currently ExpectConstructor is used to validate constructor arguments.
We do have plans to expand the features of the constructors to support:
chained constructors (one constructor calling another),
verifying that a constructor was actually called
This should be implemented in our next release that will be out in the beginning of next year.
If you wish, we will send you a preview, once the feature is complete.