You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: base.rs
    path of file: ./repos/crossbeam/crossbeam-skiplist/tests
    
    the code of the file until where you have to start completion: #![allow(clippy::redundant_clone)]

use std::ops::Bound;
use std::sync::atomic::{AtomicUsize, Ordering};

use crossbeam_epoch as epoch;
use crossbeam_skiplist::{base, SkipList};

fn ref_entry<'a, K, V>(e: impl Into<Option<base::RefEntry<'a, K, V>>>) -> Entry<'a, K, V> {
    Entry(e.into())
}
struct Entry<'a, K, V>(Option<base::RefEntry<'a, K, V>>);
impl<K, V> Entry<'_, K, V> {
    fn value(&self) -> &V {
        self.0.as_ref().unwrap().value()
    }
}
impl<K, V> Drop for Entry<'_, K, V> {
    fn drop(&mut self) {
        if let Some(e) = self.0.take() {
            e.release_with_pin(epoch::pin)
        }
    }
}

#[test]
fn new() {
    SkipList::<i32, i32>::new(epoch::default_collector().clone());
    SkipList::<String, Box<i32>>::new(epoch::default_collector().clone());
}

#[test]
fn is_empty() {
    let guard = &epoch::pin();
    let s = SkipList::new(epoch::default_collector().clone());
    assert!(s.is_empty());

    s.insert(1, 10, guard).release(guard);
    assert!(!s.is_empty());
    s.insert(2, 20, guard).release(guard);
    s.insert(3, 30, guard).release(guard);
    assert!(!s.is_empty());

    s.remove(&2, guard).unwrap().release(guard);
    assert!(!s.is_empty());

    s.remove(&1, guard).unwrap().release(guard);
    assert!(!s.is_empty());

    s.remove(&3, guard).unwrap().release(guard);
    assert!(s.is_empty());
}

#[test]
fn insert() {
    let guard = &epoch::pin();
    let insert = [0, 4, 2, 12, 8, 7, 11, 5];
    let not_present = [1, 3, 6, 9, 10];
    let s = SkipList::new(epoch::default_collector().clone());

    for &x in &insert {
        s.insert(x, x * 10, guard).release(guard);
        assert_eq!(*s.get(&x, guard).unwrap().value(), x * 10);
    }

    for &x in &not_present {
        assert!(s.get(&x, guard).is_none());
    }
}

#[test]
fn remove() {
    let guard = &epoch::pin();
    let insert = [0, 4,
    
fn upper_bound() {
    let guard = &epoch::pin();
    let s = SkipList::new(epoch::default_collector().clone());
    s.insert(30, 3, guard).release(guard);
    s.insert(50, 5, guard).release(guard);
    s.insert(10, 1, guard).release(guard);
    s.insert(40, 4, guard).release(guard);
    s.insert(20, 2, guard).release(guard);

    assert_eq!(*s.upper_bound(Bound::Unbounded, guard).unwrap().value(), 5);

    assert_eq!(
        *s.upper_bound(Bound::Included(&10), guard).unwrap().value(),
        1
    );
    assert_eq!(
        *s.upper_bound(Bound::Included(&20), guard).unwrap().value(),
        2
    );
    assert_eq!(
        *s.upper_bound(Bound::Included(&30), guard).unwrap().value(),
        3
    );
    assert_eq!(
        *s.upper_bound(Bound::Included(&40), guard).unwrap().value(),
        4
    );
    assert_eq!(
        *s.upper_bound(Bound::Included(&50), guard).unwrap().value(),
        5
    );

    assert!(s.upper_bound(Bound::Included(&7), guard).is_none());
    assert_eq!(
        *s.upper_bound(Bound::Included(&27), guard).unwrap().value(),
        2
    );
    assert_eq!(
        *s.upper_bound(Bound::Included(&31), guard).unwrap().value(),
        3
    );
    assert_eq!(
        *s.upper_bound(Bound::Included(&97), guard).unwrap().value(),
        5
    );

    assert!(s.upper_bound(Bound::Excluded(&10), guard).is_none());
    assert_eq!(
        *s.upper_bound(Bound::Excluded(&20), guard).unwrap().value(),
        1
    );
    assert_eq!(
        *s.upper_bound(Bound::Excluded(&30), guard).unwrap().value(),
        2
    );
    assert_eq!(
        *s.upper_bound(Bound::Excluded(&40), guard).unwrap().value(),
        3
    );
    assert_eq!(
        *s.upper_bound(Bound::Excluded(&50), guard).unwrap().value(),
        4
    );

    assert!(s.upper_bound(Bound::Excluded(&7), guard).is_none());
    assert_eq!(
        *s.upper_bound(Bound::Excluded(&27), guard).unwrap().value(),
        2
    );
    assert_eq!(
        *s.upper_bound(Bound::Excluded(&31), guard).unwrap().value(),
        3
    );
    assert_eq!(
        *s.upper_bound(Bound::Excluded(&97), guard).unwrap().value(),
        5
    );
}