Comment by 9rx

You are missing that HN accounts needlessly overthink everything, perhaps?

Otherwise, I doubt it. They have to write the tests again no matter what. Given that, there is no downside to reimplementing it while they are at it. All while there is a big upside to doing that: Trying to test something after the implementation is already written never ends well.

That does not guarantee that their approach will succeed. It is hard problem no matter how you slice it. But trying to reverse engineer the tests for the C version now that all knowledge of what went into it in the first place is lost is all but guaranteed to fail. Testing after the fact never ends well. Rewriting the implementation and tests in parallel increases the chances of success.