@Test
public void testMapValue() {

    final Map<String, Integer> refMap = new LinkedHashMap<>();
    refMap.put("one", 1);
    refMap.put("two", 2);
    refMap.put("three", 3);
    List<Integer> collected = refMap.entrySet().stream()
            .map(mapValue(number -> number * 2))
            .map(Map.Entry::getValue)
            .collect(Collectors.toList());
    assertEquals("mapValue should result in same list",
            Arrays.asList(2, 4, 6), collected);
}