Failing actix test

main.rs

use actix_web::{App, web, get, HttpResponse, HttpServer};
use std::sync::Mutex;

struct AppStateWithCounter {
    counter: Mutex<i32>, // <- Mutex is necessary to mutate safely across threads
}

#[get("/")]
async fn index(data: web::Data<AppStateWithCounter>) -> HttpResponse {
    let mut counter = data.counter.lock().unwrap(); // <- get counter's MutexGuard
    *counter += 1; // <- access counter inside MutexGuard
    HttpResponse::Ok().body(format! ("Request number: {}!", counter))
}

#[get("/again")]
async fn index2(data: web::Data<AppStateWithCounter>) -> HttpResponse {
    let mut counter = data.counter.lock().unwrap(); // <- get counter's MutexGuard
    *counter += 1; // <- access counter inside MutexGuard
    HttpResponse::Ok().body(format! ("Request number: {}, again!", counter))
}

#[actix_rt::main]
async fn main() -> std::io::Result<()> {
    let counter = web::Data::new(AppStateWithCounter {
        counter: Mutex::new(0),
    });

    HttpServer::new(move || {
        App::new()
            .app_data(counter.clone())
            .service(index)
            .service(index2)
    })
        .bind("127.0.0.1:8088")?
        .run()
        .await
}

#[cfg(test)]
mod tests {
    use super::*;
    use actix_web::{http};

    #[actix_rt::test]
    async fn test_index_status_code() {
        let counter = web::Data::new(AppStateWithCounter {
            counter: Mutex::new(0),
        });

        let resp = index(counter).await;
        assert_eq!(resp.status(), http::StatusCode::OK);
    }

    #[actix_rt::test]
    async fn test_index_body() {
        let counter = web::Data::new(AppStateWithCounter {
            counter: Mutex::new(0),
        });

        let resp = index(counter).await;
        let (body, mut resp) = resp.take_body().into_future().await;
        assert_eq!(body, "moi");
    }
}

Error message from test shows

✗ cargo test
   Compiling challenge v0.1.0 (/Users/wseobseo/compensate-api-challenge)
error[E0618]: expected function, found `index`
  --> src/main.rs:50:20
   |
8  | #[get("/")]
   | ----------- `index` defined here
...
50 |         let resp = index(counter).await;
   |                    ^^^^^---------
   |                    |
   |                    call expression requires function

error[E0618]: expected function, found `index`
  --> src/main.rs:60:20
   |
8  | #[get("/")]
   | ----------- `index` defined here
...
60 |         let resp = index(counter).await;
   |                    ^^^^^---------
   |                    |
   |                    call expression requires function

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0618`.
error: could not compile `challenge`.

To learn more, run the command again with --verbose.