Actually, that's not how tests work. Writing a test after the code has been produced should not be considered a real test. Let me quote Robert C. Martin on this.
If we lose the production code, we end up with a better designed system that stays clean because it has tests. If we lose the tests, then the production code rots and the team slows down in a never ending spiral of lost productivity.
So we can conclude that if it became a choice between the tests or the production code, we'd rather preserve the tests. And this means that the tests are a more important component of the system than the production code is. Because the tests are the specs.