Mixmax doesn't have a built-in A/B testing feature for sequences, but you can run your own comparison by duplicating a sequence and splitting your recipients between the two versions.
Steps
Create your first sequence with the messaging and timing you want to test (Version A).
Copy the sequence to create Version B.
Modify the variable you want to test (subject line, message body, timing, number of stages, etc.).
Split your recipient list roughly in half and add each half to the respective sequence.
After both sequences have run, compare results using sequence reports — look at open rates, reply rates, and meeting-booked rates.
Tips for a clean comparison
Only change one variable at a time so you know what drove the difference.
Use a similar recipient profile in both groups for fair results.
Run both sequences over the same time period to avoid timing bias.