class RSpec::Mocks::MethodReference

def unimplemented?

both `implemented?` and `unimplemented?` will return false.
cases when we don't know if a method is implemented and
This is not simply the inverse of `implemented?`: there are

will result in a `NoMethodError`.
Returns true if we definitively know that sending the method 
def unimplemented?
  @object_reference.when_loaded do |_m|
    return !implemented?
  end
  # If it's not loaded, then it may be implemented but we can't check.
  false
end