@Test
public void test() {

  ScoreDistribution result = ScoreDistributions.merge(dist1, dist2);
  assertEquals(2, result.getNumTerms());
  assertEquals("[HP:1, HP:2]", ImmutableSortedSet.copyOf(result.getObjectIds()).toString());
  assertEquals(tid1, result.getObjectScoreDistribution(tid1).getObjectId());
  assertEquals(tid2, result.getObjectScoreDistribution(tid2).getObjectId());
}