Six including the free one/sample.
That being said, the MGMAT folks WILL reset the tests for you after you finish the six. There is a chance of repeat questions after resetting (MGMAT guarantees no repeats in the tests as you progress 1-6).
Strategy Discussion Thread | Strategy Master | GMAT Debrief| Please discuss strategies in discussion thread. Master thread will be updated accordingly. | GC Member Write Ups
GMAT Club Premium Membership - big benefits and savings