1 is claude-code1, outputs tests as text.

2. Dumped into a file.

3. claude-code that converts this to tests in the target language, and implements the app that passes the tests.

3 is no longer hard - look at all the reimplementations from ccc, to rewrites popping up. They all have a well defined test suite as common theme. So much so that tldraw author raised a (joke) issue to remove tests from the project.