#[cfg(test)]
mod tests {
    use arrow_array::builder::{GenericListBuilder, StringDictionaryBuilder};
    use arrow_array::cast::AsArray;
    use arrow_array::types::Int32Type;
    use arrow_array::{ArrayRef, StringArray};
    use std::hash::Hash;
    use std::sync::Arc;

    #[test]
    fn it_works() {
        let scalars = vec![
            create_list_of_dict(vec![Some("a")]),
            create_list_of_dict(vec![Some("a")]),
            create_list_of_dict(vec![Some("b")]),
        ];
        let arrays = scalars.iter().map(|a| a.as_ref()).collect::<Vec<_>>();
        let concat_res = arrow::compute::concat(arrays.as_slice()).unwrap();

        let list = concat_res.as_list::<i32>();

        let dict = list.values().as_dictionary::<Int32Type>().downcast_dict::<StringArray>().unwrap();
        println!("{:?}", dict);

        let values = dict.values().iter().collect::<Vec<_>>();
        let mut unique_values = values.clone();
        unique_values.dedup();
        assert_eq!(values, unique_values, "There are duplicates in the value list");
    }

    fn create_list_of_dict(items: Vec<Option<&'static str>>) -> ArrayRef {
        let mut builder = GenericListBuilder::<i32, _>::new(StringDictionaryBuilder::<Int32Type>::new());

        for item in items {
            builder.values().append_option(item);
        }

        builder.append(true);

        Arc::new(builder.finish())
    }

}