@Test
void testReduce1() {

    final Map.Entry<String, Integer> expected = entry("jedandvatri", 1 + 2 + 3);
    final Map.Entry<String, Integer> actual = instance.reduce(entry("", 0), (e0, e1) -> entry(e0.getKey()+e1.getKey() , e0.getValue()+e1.getValue()), (e0, e1) -> entry(e0.getKey()+e1.getKey() , e0.getValue()+e1.getValue()));
    assertEquals(expected, actual);
}