@Test
public void clear() throws Exception {

    multiMap.putAll(ImmutableListMultimap.of(
            "first", new TestEntity("1", "v1"),
            "second", new TestEntity("2", "v2"),
            "second", new TestEntity("3", "v3")
    ));
    assertThat(multiMap.asMap()).isNotEmpty();
    multiMap.clear();
    assertThat(multiMap.asMap()).isEmpty();
}