public void testSort() { long[][] ars = {{}, {0,1,2}, {2,4,6}, {0,1}, {5,7,9}, {-1, 1, 2}, {0}, {10}, {0,1,2,3}}; LongArray[] arrays = new LongArray[ars.length + 1]; for (int i = 0; i < ars.length; i++) { arrays[i] = new LongArray(ars[i]); } arrays[ars.length] = null; Arrays.sort(arrays, comparator); StringBuilder sb = new StringBuilder(); for (LongArray array: arrays) { LongCollections.append(sb, array); } assertEquals("" + "null" + "()" + "(-1, 1, 2)" + "(0)(0, 1)" + "(0, 1, 2)" + "(0, 1, 2, 3)" + "(2, 4, 6)" + "(5, 7, 9)" + "(10)", sb.toString()); }