### Question:
MathUtils { public static List<Integer> positive(List<Integer> vals) { return vals.stream().filter(val -> val > 0).collect(Collectors.toList()); }  static Integer sum(List<Integer> vals); static List<Integer> positive(List<Integer> vals); static List<Integer> negative(List<Integer> vals);  }### Answer:
@Test @DisplayName("should get positive values") void positiveTest() { var positiveValues = MathUtils.positive(vals); assertEquals(positiveValues, List.of(2, 1, 3)); }