Why does A/B testing cause 'dedupe by email' to fail when sending CiviMail to contacts with same email address

Question

Client is asking why 4 emails have been delivered to 4 contacts who all have same address.

Test1: tested with 2 contacts and didn't use A/B testing.

Outcome: was told would be delivered to ~1 address and was only 1 delivered - GOOD

Test2: tested with same 2 contacts with A/B - 50% to A and 50% to B (so no FINAL mailing)

Outcome: was told would be delivered to ~1 address and was only 1 delivered (to A mailing) - GOOD

Test3: tested with 4 contacts sharing same email with A/B - 25% to A and 25% to B and 50% to FINAL

Outcome: was told would be delivered to ~1 address. Had 1 delivered (to A mailing), 1 delivered to B mailing, and 1 delivered to Final mailing - BAD

So I think A/B testing is causing 'dedupe by email' to break

Answer 1

From what you describe it sounds like the deduping is happening within each group rather than before the recipients are split into A, B and final groups.

You could confirm this by doing:

Test 4: 8 contacts sharing same email with A/B - 25% to A and 25% to B and 50% to FINAL

I would expect the same results as for test 3: 1 delivered to A mailing, 1 delivered to B mailing, and 1 delivered to Final mailing.