That's fine, because sid is basically always the firehose of new packages. sid is always equivalent to unstable, so neither matters. But "testing" is dynamic.

That's fine, because sid is basically always the firehose of new packages. sid is always equivalent to unstable, so neither matters. But "testing" is dynamic. Before the release it's lenny, after the release it'll surprise-upgrade itself to whatever sid was at the branching point.