@Test
void testCreateWithUnnecessaryReduction() {

    ImmutableMap<String, Integer> toReduce = ImmutableMap.of(
            "A", 1,
            "B", 2,
            "C", 3,
            "D", 4);
    ImmutableMap<String, Integer> reduced = ImmutableMapFactory.createAndReduceCollisions(
            toReduce,
            s -> s.substring(0, 1),
            i -> i,
            0,
            Integer::sum);
    ImmutableMap<String, Integer> expected = ImmutableMap.of(
            "A", 1,
            "B", 2,
            "C", 3,
            "D", 4);
    Assertions.assertEquals(expected, reduced);
}