With fork in Test := true, two different sets of Frameworks & Runners appear to be instantiated: I'm guessing one in the original process, one in the forked process. Both .done() methods get called, but it is the runner without all the test information who's done() method gets printed. Hence if you were relying on your Runner/Task to aggregate information and print it out at the end of the test session, with fork in Test := true returning it from done doesn't work: e.g. in the case of uTest, which prints a nice test-summary and failure-summary, the summary shows "0 tests" when fork in Test := true

Workaround: use println in the .done() method to print the done message myself. I lose all the [info] spam in the LHS of the terminal when I do this, but it's not a huge loss...