.buildOrThrow();

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

  // TODO(b/172823566): Use mainline testToImmutableBiMap once CollectorTester is usable to java7.
  public void testToImmutableBiMap_java7_combine() {
    ImmutableBiMap.Builder<String, Integer> zis =