assertThrows(IllegalArgumentException.class, () -> zis.combine(zat).build());
  }

  // BiMap-specific tests

  @SuppressWarnings("DoNotCall")
  public void testForcePut() {
    BiMap<String, Integer> bimap = ImmutableBiMap.copyOf(ImmutableMap.of("one", 1, "two", 2));
    assertThrows(UnsupportedOperationException.class, () -> bimap.forcePut("three", 3));
  }