Comment by soraminazuki

Presumably, in any sane process, changes would be split into small, reviewable PRs with people reasoning about the code. That wouldn't eliminate the possibility of bugs, but when done correctly it would give us substantially higher confidence that semantic equivalence is preserved.

With zero reviews and no one even reading the code, there's zero confidence. For all we know, the new Bun could contain a change that causes JS file reads to return a novel for a very specific filename, and the tests people keep pointing to, intended to downplay the malpractice, would never catch it. Tests cannot cover every contrived scenario that normal human beings would never think of writing.