@Test
public void testRecommendedBecause() throws Exception {

  ItemBasedRecommender recommender = buildRecommender2();
  List<RecommendedItem> recommendedBecause = recommender.recommendedBecause(1, 4, 3);
  assertNotNull(recommendedBecause);
  assertEquals(3, recommendedBecause.size());
  RecommendedItem first = recommendedBecause.get(0);
  RecommendedItem second = recommendedBecause.get(1);
  RecommendedItem third = recommendedBecause.get(2);
  assertEquals(2, first.getItemID());
  assertEquals(0.99f, first.getValue(), EPSILON);
  assertEquals(3, second.getItemID());
  assertEquals(0.4f, second.getValue(), EPSILON);
  assertEquals(0, third.getItemID());
  assertEquals(0.2f, third.getValue(), EPSILON);
}