### Question:
MathUtils { public static Integer sum(List<Integer> vals) { var sum = vals.stream().reduce(Integer::sum); return sum.get(); }  static Integer sum(List<Integer> vals); static List<Integer> positive(List<Integer> vals); static List<Integer> negative(List<Integer> vals);  }### Answer:
@Test @DisplayName("testing sum of values") void sumTest() { var sum = MathUtils.sum(vals); assertEquals(Integer.valueOf(2), sum); }