@Test
public void testMapEntry() {

    final Map<String, Integer> refMap = new LinkedHashMap<>();
    refMap.put("one", 1);
    refMap.put("two", 2);
    refMap.put("three", 3);
    List<String> collected = refMap.entrySet().stream()
            .map(mapEntry((string, number) -> string + "_" + number)).collect(Collectors.toList());
    assertEquals("mapEntry should result in same list",
            Arrays.asList("one_1", "two_2", "three_3"), collected);
}