This looks like a bug in the making since forgetting to reset these can produce unexpected results. message and header are only used on a per-message basis, so why are they class members?
I don't know what version 10300 is or why it's useful to test. Please give it a useful name.
This test is hard to follow because the seeder is sending a message to itself with the vAddr list that it already has. This "works" but the intent is impossible to follow. The test should explicitly send some number of addresses to the seeder and test against that expectation. Otherwise you look at this test with no way of knowing what the right behavior should be.