.onResultOf((ImmutableListMultimap<?, ?> mm) -> mm.asMap().entrySet().asList())
            .and(Equivalence.equals());
    CollectorTester.of(collector, equivalence)
        .expectCollects(ImmutableListMultimap.of())
        .expectCollects(
            ImmutableListMultimap.of("a", 1, "b", 2, "a", 3, "c", 4),
            mapEntry("a", 1),
            mapEntry("b", 2),
            mapEntry("a", 3),