assertTrue(multimap().putAll(source));
    assertTrue(multimap().containsEntry(null, v0()));
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPutAllRejectsNullValue() {
    Multimap<K, V> source = getSubjectGenerator().create(mapEntry(k0(), null));
    assertThrows(NullPointerException.class, () -> multimap().putAll(source));
    expectUnchanged();
  }