How do I unit test a struct that wraps a Postgres client?

Solution for How do I unit test a struct that wraps a Postgres client?
is Given Below:

I am wrapping a deadpool-postgres client in my own struct:

struct Data {
    pool: std::collections::HashMap<String, deadpool_postgres::Pool>,
}

impl Data {
    pub fn create(config: Configuration) -> Data {
        todo!()
    }

    pub async fn get_client(&self, key: &str) -> Option<deadpool_postgres::Client> {
        return Some(self.pool.get(key).get().await.unwrap());
    }
}

#[cfg(test)]
mod tests {
    #[test]
    fn test() {
        let data = Data::create(config);
        let client = data.get_client("default");
        // how to test here?
        // assert!( ... );
    }
}

I have added tokio-test to my dev-dependencies but I have not been able complete this test.