Empty#filter{,Acc}, NonEmpty#filter{,.Acc}, union

[info] TweetSetSuite:
[info] - filter: on empty set
[info] - filter: a on set5
[info] - filter: 20 on set5
[info] - union: set4c and set4d
[info] - union: with empty set (1)
[info] - union: with empty set (2)
[info] - descending: set5 *** FAILED ***
[info]   org.scalatest.exceptions.TestFailedException was thrown. (TweetSetSuite.scala:68)
[error] Failed: : Total 7, Failed 1, Errors 0, Passed 6, Skipped 0
[error] Failed tests:
[error] 	objsets.TweetSetSuite
[trace] Stack trace suppressed: run last assignment/test:test for the full output.
[error] (assignment/test:test) Tests unsuccessful
[error] Total time: 1 s, completed Apr 12, 2013 6:54:56 PM