As Corbyn said then, we're better off in the EU. As he said since, he'd vote Remain again if it comes to another referendum.
Labour policy is that the referendum gave a mandate to try to negotiate acceptable term for leaving - and no further than that.
So, the 6 Tests as guidelines to judge what's acceptable.
The political choice is then the strategy to be able to get a majority to reject a bad deal - the key vote. You can go the LibDem way and say that you respect the referendum mandate but won't accept any deal whatsoever.
That you'll vote against the deal to bring on a new referendum so you can exit-from-brexit.
Or you can act as if you really do want government to negotiate an acceptable deal. But prepare to block a bad deal. This latter strategy stands more chance of success ... because ...
... Tory 'rebels' will not defy the immense pressure from government, Party and whips to vote for anything you can hang a 'stop brexit' label on. So in the crucial 'big vote' the Labour opposition can present itself as the Party that supported the majority advice.
But point out that when they supported notifying A50(2) intention to leave, to start negotiations, it was on the basis of Government promises (Test 2) that haven't been delivered.
Labour will probably have to come to some tacit agreement with Tories that rejecting the deal isn't de facto a vote to Remain. Otherwise those Tories will obey their Party whip. In the past Labour has promised not to make it a Confidence issue, and to support renegotiation.
All totally unsatisfactory to those who think that if enough sign the People's Vote petition then brexit will end.
But unless Tory MPs, who won't at this stage vote against brexit, actually do vote against the brexit deal, then we're out.
Reject the deal = new openings.