How does jest work inside?

One of these days, I got myself thinking about the magic inside jest (our beloved JavaScript testing framework). How do the functions test, expect, mock, and spyOn work? I tried then to replicate it and create my own implementation of Jest functions, we will name it flaviest 😂. Let’s see the magic: Test functionLet’s start with the basic structure of a test, the test method itself. I need to be a