[angio]

It's a repl, so you build the final output incrementally. Testing becomes part of the development workflow like you would do in languages that rely on the repl like lisps.

For example, you start with the inputs and you apply the first layer of transformations, then check what it does makes sense. Then maybe you refactor it out in its own function and add the generated test for it. Then you move on the next step and so on until you have the final result.