IllegalArgumentException expected =
        assertThrows(IllegalArgumentException.class, () -> ImmutableBiMap.copyOf(map));
    assertThat(expected.getMessage()).containsMatch("1|2");
  }

  public void testToImmutableBiMap() {
    Collector<Entry<String, Integer>, ?, ImmutableBiMap<String, Integer>> collector =
        toImmutableBiMap(Entry::getKey, Entry::getValue);
    Equivalence<ImmutableBiMap<String, Integer>> equivalence =