assertThrows(
        NullPointerException.class, () -> builder.putAll((Multimap<String, Integer>) toPut));
  }

  public void testBuilderPutNullValue() {
    Multimap<String, @Nullable Integer> toPut = LinkedListMultimap.create();
    toPut.put("foo", null);
    ImmutableListMultimap.Builder<String, Integer> builder = ImmutableListMultimap.builder();

  }

  public void testBuilderPutNullKey() {
    Builder<String, Integer> builder = new Builder<>();
    assertThrows(NullPointerException.class, () -> builder.put(null, 1));
  }

  public void testBuilderPutNullValue() {
    Builder<String, Integer> builder = new Builder<>();
    assertThrows(NullPointerException.class, () -> builder.put("one", null));
  }

  public void testBuilderPutNullKeyViaPutAll() {