@Test public void flattenShouldReturnCollectionContainingAllSuppliedValues() { final Collection<Collection<Integer>> is = new ArrayList<>(); is.add(Arrays.asList(1, 2, 3, 4, 5)); is.add(Arrays.asList(6, 7, 8, 9)); assertEquals(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9), FCollection.flatten(is)); }