Doctoral supervision has been described through a number of models useful for understanding different aspects of supervision. None of these are all-encompassing, but each emphasizes a particular perspective, like the relationship, personal vs. structural support, process vs. product orientation. In running courses for doctoral supervisors, one aspect that escapes attention when using these mental models is assessment, and such model can support new supervisors in reflecting on how to build autonomy. There is a body of research into the PhD examination, but this has not been translated into formative assessment during the PhD process. This proposal aims to fill that need by suggesting a mental model of supervision as formative assessment.