Rollup merge of #135621 - bjorn3:move_tests_to_stdtests, r=Noratrieb

Move some std tests to integration tests

Unit tests directly inside of standard library crates require a very fragile way of building that is hard to reproduce outside of bootstrap.

Follow up to https://github.com/rust-lang/rust/pull/133859

20 files changed, 8 insertions, 4130 deletions

diff --git a/library/std/src/sync/barrier.rs b/library/std/src/sync/barrier.rs
index 862753e4765..067ff66d9af 100644
--- a/library/std/src/sync/barrier.rs
+++ b/library/std/src/sync/barrier.rs
@@ -1,6 +1,3 @@
-#[cfg(test)]
-mod tests;
-
 use crate::fmt;
 // FIXME(nonpoison_mutex,nonpoison_condvar): switch to nonpoison versions once they are available
 use crate::sync::{Condvar, Mutex};
diff --git a/library/std/src/sync/barrier/tests.rs b/library/std/src/sync/barrier/tests.rs
deleted file mode 100644
index 0fbcd998812..00000000000
--- a/library/std/src/sync/barrier/tests.rs
+++ /dev/null
@@ -1,35 +0,0 @@
-use crate::sync::mpsc::{TryRecvError, channel};
-use crate::sync::{Arc, Barrier};
-use crate::thread;
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn test_barrier() {
-    const N: usize = 10;
-
-    let barrier = Arc::new(Barrier::new(N));
-    let (tx, rx) = channel();
-
-    for _ in 0..N - 1 {
-        let c = barrier.clone();
-        let tx = tx.clone();
-        thread::spawn(move || {
-            tx.send(c.wait().is_leader()).unwrap();
-        });
-    }
-
-    // At this point, all spawned threads should be blocked,
-    // so we shouldn't get anything from the port
-    assert!(matches!(rx.try_recv(), Err(TryRecvError::Empty)));
-
-    let mut leader_found = barrier.wait().is_leader();
-
-    // Now, the barrier is cleared and we should get data.
-    for _ in 0..N - 1 {
-        if rx.recv().unwrap() {
-            assert!(!leader_found);
-            leader_found = true;
-        }
-    }
-    assert!(leader_found);
-}
diff --git a/library/std/src/sync/lazy_lock.rs b/library/std/src/sync/lazy_lock.rs
index 98c83d8d326..78cf8841efe 100644
--- a/library/std/src/sync/lazy_lock.rs
+++ b/library/std/src/sync/lazy_lock.rs
@@ -350,6 +350,3 @@ unsafe impl<T: Sync + Send, F: Send> Sync for LazyLock<T, F> {}
 impl<T: RefUnwindSafe + UnwindSafe, F: UnwindSafe> RefUnwindSafe for LazyLock<T, F> {}
 #[stable(feature = "lazy_cell", since = "1.80.0")]
 impl<T: UnwindSafe, F: UnwindSafe> UnwindSafe for LazyLock<T, F> {}
-
-#[cfg(test)]
-mod tests;
diff --git a/library/std/src/sync/lazy_lock/tests.rs b/library/std/src/sync/lazy_lock/tests.rs
deleted file mode 100644
index 7d7dde54349..00000000000
--- a/library/std/src/sync/lazy_lock/tests.rs
+++ /dev/null
@@ -1,167 +0,0 @@
-use crate::cell::LazyCell;
-use crate::sync::atomic::AtomicUsize;
-use crate::sync::atomic::Ordering::SeqCst;
-use crate::sync::{LazyLock, Mutex, OnceLock};
-use crate::{panic, thread};
-
-fn spawn_and_wait<R: Send + 'static>(f: impl FnOnce() -> R + Send + 'static) -> R {
-    thread::spawn(f).join().unwrap()
-}
-
-#[test]
-fn lazy_default() {
-    static CALLED: AtomicUsize = AtomicUsize::new(0);
-
-    struct Foo(u8);
-    impl Default for Foo {
-        fn default() -> Self {
-            CALLED.fetch_add(1, SeqCst);
-            Foo(42)
-        }
-    }
-
-    let lazy: LazyCell<Mutex<Foo>> = <_>::default();
-
-    assert_eq!(CALLED.load(SeqCst), 0);
-
-    assert_eq!(lazy.lock().unwrap().0, 42);
-    assert_eq!(CALLED.load(SeqCst), 1);
-
-    lazy.lock().unwrap().0 = 21;
-
-    assert_eq!(lazy.lock().unwrap().0, 21);
-    assert_eq!(CALLED.load(SeqCst), 1);
-}
-
-#[test]
-#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn lazy_poisoning() {
-    let x: LazyCell<String> = LazyCell::new(|| panic!("kaboom"));
-    for _ in 0..2 {
-        let res = panic::catch_unwind(panic::AssertUnwindSafe(|| x.len()));
-        assert!(res.is_err());
-    }
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn sync_lazy_new() {
-    static CALLED: AtomicUsize = AtomicUsize::new(0);
-    static SYNC_LAZY: LazyLock<i32> = LazyLock::new(|| {
-        CALLED.fetch_add(1, SeqCst);
-        92
-    });
-
-    assert_eq!(CALLED.load(SeqCst), 0);
-
-    spawn_and_wait(|| {
-        let y = *SYNC_LAZY - 30;
-        assert_eq!(y, 62);
-        assert_eq!(CALLED.load(SeqCst), 1);
-    });
-
-    let y = *SYNC_LAZY - 30;
-    assert_eq!(y, 62);
-    assert_eq!(CALLED.load(SeqCst), 1);
-}
-
-#[test]
-fn sync_lazy_default() {
-    static CALLED: AtomicUsize = AtomicUsize::new(0);
-
-    struct Foo(u8);
-    impl Default for Foo {
-        fn default() -> Self {
-            CALLED.fetch_add(1, SeqCst);
-            Foo(42)
-        }
-    }
-
-    let lazy: LazyLock<Mutex<Foo>> = <_>::default();
-
-    assert_eq!(CALLED.load(SeqCst), 0);
-
-    assert_eq!(lazy.lock().unwrap().0, 42);
-    assert_eq!(CALLED.load(SeqCst), 1);
-
-    lazy.lock().unwrap().0 = 21;
-
-    assert_eq!(lazy.lock().unwrap().0, 21);
-    assert_eq!(CALLED.load(SeqCst), 1);
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn static_sync_lazy() {
-    static XS: LazyLock<Vec<i32>> = LazyLock::new(|| {
-        let mut xs = Vec::new();
-        xs.push(1);
-        xs.push(2);
-        xs.push(3);
-        xs
-    });
-
-    spawn_and_wait(|| {
-        assert_eq!(&*XS, &vec![1, 2, 3]);
-    });
-
-    assert_eq!(&*XS, &vec![1, 2, 3]);
-}
-
-#[test]
-fn static_sync_lazy_via_fn() {
-    fn xs() -> &'static Vec<i32> {
-        static XS: OnceLock<Vec<i32>> = OnceLock::new();
-        XS.get_or_init(|| {
-            let mut xs = Vec::new();
-            xs.push(1);
-            xs.push(2);
-            xs.push(3);
-            xs
-        })
-    }
-    assert_eq!(xs(), &vec![1, 2, 3]);
-}
-
-#[test]
-#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn sync_lazy_poisoning() {
-    let x: LazyLock<String> = LazyLock::new(|| panic!("kaboom"));
-    for _ in 0..2 {
-        let res = panic::catch_unwind(|| x.len());
-        assert!(res.is_err());
-    }
-}
-
-// Check that we can infer `T` from closure's type.
-#[test]
-fn lazy_type_inference() {
-    let _ = LazyCell::new(|| ());
-}
-
-#[test]
-fn is_sync_send() {
-    fn assert_traits<T: Send + Sync>() {}
-    assert_traits::<LazyLock<String>>();
-}
-
-#[test]
-#[should_panic = "has previously been poisoned"]
-fn lazy_force_mut_panic() {
-    let mut lazy = LazyLock::<String>::new(|| panic!());
-    crate::panic::catch_unwind(crate::panic::AssertUnwindSafe(|| {
-        let _ = LazyLock::force_mut(&mut lazy);
-    }))
-    .unwrap_err();
-    let _ = &*lazy;
-}
-
-#[test]
-fn lazy_force_mut() {
-    let s = "abc".to_owned();
-    let mut lazy = LazyLock::new(move || s);
-    LazyLock::force_mut(&mut lazy);
-    let p = LazyLock::force_mut(&mut lazy);
-    p.clear();
-    LazyLock::force_mut(&mut lazy);
-}
diff --git a/library/std/src/sync/mpmc/tests.rs b/library/std/src/sync/mpmc/tests.rs
deleted file mode 100644
index ab14050df6c..00000000000
--- a/library/std/src/sync/mpmc/tests.rs
+++ /dev/null
@@ -1,728 +0,0 @@
-use super::*;
-use crate::{env, thread};
-
-pub fn stress_factor() -> usize {
-    match env::var("RUST_TEST_STRESS") {
-        Ok(val) => val.parse().unwrap(),
-        Err(..) => 1,
-    }
-}
-
-#[test]
-fn smoke() {
-    let (tx, rx) = channel::<i32>();
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-}
-
-#[test]
-fn drop_full() {
-    let (tx, _rx) = channel::<Box<isize>>();
-    tx.send(Box::new(1)).unwrap();
-}
-
-#[test]
-fn drop_full_shared() {
-    let (tx, _rx) = channel::<Box<isize>>();
-    drop(tx.clone());
-    drop(tx.clone());
-    tx.send(Box::new(1)).unwrap();
-}
-
-#[test]
-fn smoke_shared() {
-    let (tx, rx) = channel::<i32>();
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-    let tx = tx.clone();
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-}
-
-#[test]
-fn smoke_threads() {
-    let (tx, rx) = channel::<i32>();
-    let t1 = thread::spawn(move || {
-        for i in 0..2 {
-            tx.send(i).unwrap();
-        }
-    });
-    let t2 = thread::spawn(move || {
-        assert_eq!(rx.recv().unwrap(), 0);
-        assert_eq!(rx.recv().unwrap(), 1);
-    });
-    t1.join().unwrap();
-    t2.join().unwrap();
-}
-
-#[test]
-fn smoke_port_gone() {
-    let (tx, rx) = channel::<i32>();
-    drop(rx);
-    assert!(tx.send(1).is_err());
-}
-
-#[test]
-fn smoke_shared_port_gone() {
-    let (tx, rx) = channel::<i32>();
-    drop(rx);
-    assert!(tx.send(1).is_err())
-}
-
-#[test]
-fn smoke_shared_port_gone2() {
-    let (tx, rx) = channel::<i32>();
-    drop(rx);
-    let tx2 = tx.clone();
-    drop(tx);
-    assert!(tx2.send(1).is_err());
-}
-
-#[test]
-fn port_gone_concurrent() {
-    let (tx, rx) = channel::<i32>();
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap();
-    });
-    while tx.send(1).is_ok() {}
-}
-
-#[test]
-fn port_gone_concurrent_shared() {
-    let (tx, rx) = channel::<i32>();
-    let tx2 = tx.clone();
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap();
-    });
-    while tx.send(1).is_ok() && tx2.send(1).is_ok() {}
-}
-
-#[test]
-fn smoke_chan_gone() {
-    let (tx, rx) = channel::<i32>();
-    drop(tx);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn smoke_chan_gone_shared() {
-    let (tx, rx) = channel::<()>();
-    let tx2 = tx.clone();
-    drop(tx);
-    drop(tx2);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn chan_gone_concurrent() {
-    let (tx, rx) = channel::<i32>();
-    let _t = thread::spawn(move || {
-        tx.send(1).unwrap();
-        tx.send(1).unwrap();
-    });
-    while rx.recv().is_ok() {}
-}
-
-#[test]
-fn stress() {
-    let count = if cfg!(miri) { 100 } else { 10000 };
-    let (tx, rx) = channel::<i32>();
-    let t = thread::spawn(move || {
-        for _ in 0..count {
-            tx.send(1).unwrap();
-        }
-    });
-    for _ in 0..count {
-        assert_eq!(rx.recv().unwrap(), 1);
-    }
-    t.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn stress_shared() {
-    const AMT: u32 = if cfg!(miri) { 100 } else { 10000 };
-    const NTHREADS: u32 = 8;
-    let (tx, rx) = channel::<i32>();
-
-    let t = thread::spawn(move || {
-        for _ in 0..AMT * NTHREADS {
-            assert_eq!(rx.recv().unwrap(), 1);
-        }
-        match rx.try_recv() {
-            Ok(..) => panic!(),
-            _ => {}
-        }
-    });
-
-    for _ in 0..NTHREADS {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            for _ in 0..AMT {
-                tx.send(1).unwrap();
-            }
-        });
-    }
-    drop(tx);
-    t.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn send_from_outside_runtime() {
-    let (tx1, rx1) = channel::<()>();
-    let (tx2, rx2) = channel::<i32>();
-    let t1 = thread::spawn(move || {
-        tx1.send(()).unwrap();
-        for _ in 0..40 {
-            assert_eq!(rx2.recv().unwrap(), 1);
-        }
-    });
-    rx1.recv().unwrap();
-    let t2 = thread::spawn(move || {
-        for _ in 0..40 {
-            tx2.send(1).unwrap();
-        }
-    });
-    t1.join().ok().expect("thread panicked");
-    t2.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn recv_from_outside_runtime() {
-    let (tx, rx) = channel::<i32>();
-    let t = thread::spawn(move || {
-        for _ in 0..40 {
-            assert_eq!(rx.recv().unwrap(), 1);
-        }
-    });
-    for _ in 0..40 {
-        tx.send(1).unwrap();
-    }
-    t.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn no_runtime() {
-    let (tx1, rx1) = channel::<i32>();
-    let (tx2, rx2) = channel::<i32>();
-    let t1 = thread::spawn(move || {
-        assert_eq!(rx1.recv().unwrap(), 1);
-        tx2.send(2).unwrap();
-    });
-    let t2 = thread::spawn(move || {
-        tx1.send(1).unwrap();
-        assert_eq!(rx2.recv().unwrap(), 2);
-    });
-    t1.join().ok().expect("thread panicked");
-    t2.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn oneshot_single_thread_close_port_first() {
-    // Simple test of closing without sending
-    let (_tx, rx) = channel::<i32>();
-    drop(rx);
-}
-
-#[test]
-fn oneshot_single_thread_close_chan_first() {
-    // Simple test of closing without sending
-    let (tx, _rx) = channel::<i32>();
-    drop(tx);
-}
-
-#[test]
-fn oneshot_single_thread_send_port_close() {
-    // Testing that the sender cleans up the payload if receiver is closed
-    let (tx, rx) = channel::<Box<i32>>();
-    drop(rx);
-    assert!(tx.send(Box::new(0)).is_err());
-}
-
-#[test]
-fn oneshot_single_thread_recv_chan_close() {
-    // Receiving on a closed chan will panic
-    let res = thread::spawn(move || {
-        let (tx, rx) = channel::<i32>();
-        drop(tx);
-        rx.recv().unwrap();
-    })
-    .join();
-    // What is our res?
-    assert!(res.is_err());
-}
-
-#[test]
-fn oneshot_single_thread_send_then_recv() {
-    let (tx, rx) = channel::<Box<i32>>();
-    tx.send(Box::new(10)).unwrap();
-    assert!(*rx.recv().unwrap() == 10);
-}
-
-#[test]
-fn oneshot_single_thread_try_send_open() {
-    let (tx, rx) = channel::<i32>();
-    assert!(tx.send(10).is_ok());
-    assert!(rx.recv().unwrap() == 10);
-}
-
-#[test]
-fn oneshot_single_thread_try_send_closed() {
-    let (tx, rx) = channel::<i32>();
-    drop(rx);
-    assert!(tx.send(10).is_err());
-}
-
-#[test]
-fn oneshot_single_thread_try_recv_open() {
-    let (tx, rx) = channel::<i32>();
-    tx.send(10).unwrap();
-    assert!(rx.recv() == Ok(10));
-}
-
-#[test]
-fn oneshot_single_thread_try_recv_closed() {
-    let (tx, rx) = channel::<i32>();
-    drop(tx);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn oneshot_single_thread_peek_data() {
-    let (tx, rx) = channel::<i32>();
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Empty));
-    tx.send(10).unwrap();
-    assert_eq!(rx.try_recv(), Ok(10));
-}
-
-#[test]
-fn oneshot_single_thread_peek_close() {
-    let (tx, rx) = channel::<i32>();
-    drop(tx);
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Disconnected));
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Disconnected));
-}
-
-#[test]
-fn oneshot_single_thread_peek_open() {
-    let (_tx, rx) = channel::<i32>();
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Empty));
-}
-
-#[test]
-fn oneshot_multi_task_recv_then_send() {
-    let (tx, rx) = channel::<Box<i32>>();
-    let _t = thread::spawn(move || {
-        assert!(*rx.recv().unwrap() == 10);
-    });
-
-    tx.send(Box::new(10)).unwrap();
-}
-
-#[test]
-fn oneshot_multi_task_recv_then_close() {
-    let (tx, rx) = channel::<Box<i32>>();
-    let _t = thread::spawn(move || {
-        drop(tx);
-    });
-    let res = thread::spawn(move || {
-        assert!(*rx.recv().unwrap() == 10);
-    })
-    .join();
-    assert!(res.is_err());
-}
-
-#[test]
-fn oneshot_multi_thread_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel::<i32>();
-        let _t = thread::spawn(move || {
-            drop(rx);
-        });
-        drop(tx);
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_send_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel::<i32>();
-        let _t = thread::spawn(move || {
-            drop(rx);
-        });
-        let _ = thread::spawn(move || {
-            tx.send(1).unwrap();
-        })
-        .join();
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_recv_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel::<i32>();
-        thread::spawn(move || {
-            let res = thread::spawn(move || {
-                rx.recv().unwrap();
-            })
-            .join();
-            assert!(res.is_err());
-        });
-        let _t = thread::spawn(move || {
-            thread::spawn(move || {
-                drop(tx);
-            });
-        });
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_send_recv_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel::<Box<isize>>();
-        let _t = thread::spawn(move || {
-            tx.send(Box::new(10)).unwrap();
-        });
-        assert!(*rx.recv().unwrap() == 10);
-    }
-}
-
-#[test]
-fn stream_send_recv_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel();
-
-        send(tx, 0);
-        recv(rx, 0);
-
-        fn send(tx: Sender<Box<i32>>, i: i32) {
-            if i == 10 {
-                return;
-            }
-
-            thread::spawn(move || {
-                tx.send(Box::new(i)).unwrap();
-                send(tx, i + 1);
-            });
-        }
-
-        fn recv(rx: Receiver<Box<i32>>, i: i32) {
-            if i == 10 {
-                return;
-            }
-
-            thread::spawn(move || {
-                assert!(*rx.recv().unwrap() == i);
-                recv(rx, i + 1);
-            });
-        }
-    }
-}
-
-#[test]
-fn oneshot_single_thread_recv_timeout() {
-    let (tx, rx) = channel();
-    tx.send(()).unwrap();
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Ok(()));
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Err(RecvTimeoutError::Timeout));
-    tx.send(()).unwrap();
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Ok(()));
-}
-
-#[test]
-fn stress_recv_timeout_two_threads() {
-    let (tx, rx) = channel();
-    let stress = stress_factor() + 100;
-    let timeout = Duration::from_millis(100);
-
-    thread::spawn(move || {
-        for i in 0..stress {
-            if i % 2 == 0 {
-                thread::sleep(timeout * 2);
-            }
-            tx.send(1usize).unwrap();
-        }
-    });
-
-    let mut recv_count = 0;
-    loop {
-        match rx.recv_timeout(timeout) {
-            Ok(n) => {
-                assert_eq!(n, 1usize);
-                recv_count += 1;
-            }
-            Err(RecvTimeoutError::Timeout) => continue,
-            Err(RecvTimeoutError::Disconnected) => break,
-        }
-    }
-
-    assert_eq!(recv_count, stress);
-}
-
-#[test]
-fn recv_timeout_upgrade() {
-    let (tx, rx) = channel::<()>();
-    let timeout = Duration::from_millis(1);
-    let _tx_clone = tx.clone();
-
-    let start = Instant::now();
-    assert_eq!(rx.recv_timeout(timeout), Err(RecvTimeoutError::Timeout));
-    assert!(Instant::now() >= start + timeout);
-}
-
-#[test]
-fn stress_recv_timeout_shared() {
-    let (tx, rx) = channel();
-    let stress = stress_factor() + 100;
-
-    for i in 0..stress {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            thread::sleep(Duration::from_millis(i as u64 * 10));
-            tx.send(1usize).unwrap();
-        });
-    }
-
-    drop(tx);
-
-    let mut recv_count = 0;
-    loop {
-        match rx.recv_timeout(Duration::from_millis(10)) {
-            Ok(n) => {
-                assert_eq!(n, 1usize);
-                recv_count += 1;
-            }
-            Err(RecvTimeoutError::Timeout) => continue,
-            Err(RecvTimeoutError::Disconnected) => break,
-        }
-    }
-
-    assert_eq!(recv_count, stress);
-}
-
-#[test]
-fn very_long_recv_timeout_wont_panic() {
-    let (tx, rx) = channel::<()>();
-    let join_handle = thread::spawn(move || rx.recv_timeout(Duration::from_secs(u64::MAX)));
-    thread::sleep(Duration::from_secs(1));
-    assert!(tx.send(()).is_ok());
-    assert_eq!(join_handle.join().unwrap(), Ok(()));
-}
-
-#[test]
-fn recv_a_lot() {
-    let count = if cfg!(miri) { 1000 } else { 10000 };
-    // Regression test that we don't run out of stack in scheduler context
-    let (tx, rx) = channel();
-    for _ in 0..count {
-        tx.send(()).unwrap();
-    }
-    for _ in 0..count {
-        rx.recv().unwrap();
-    }
-}
-
-#[test]
-fn shared_recv_timeout() {
-    let (tx, rx) = channel();
-    let total = 5;
-    for _ in 0..total {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            tx.send(()).unwrap();
-        });
-    }
-
-    for _ in 0..total {
-        rx.recv().unwrap();
-    }
-
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Err(RecvTimeoutError::Timeout));
-    tx.send(()).unwrap();
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Ok(()));
-}
-
-#[test]
-fn shared_chan_stress() {
-    let (tx, rx) = channel();
-    let total = stress_factor() + 100;
-    for _ in 0..total {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            tx.send(()).unwrap();
-        });
-    }
-
-    for _ in 0..total {
-        rx.recv().unwrap();
-    }
-}
-
-#[test]
-fn test_nested_recv_iter() {
-    let (tx, rx) = channel::<i32>();
-    let (total_tx, total_rx) = channel::<i32>();
-
-    let _t = thread::spawn(move || {
-        let mut acc = 0;
-        for x in rx.iter() {
-            acc += x;
-        }
-        total_tx.send(acc).unwrap();
-    });
-
-    tx.send(3).unwrap();
-    tx.send(1).unwrap();
-    tx.send(2).unwrap();
-    drop(tx);
-    assert_eq!(total_rx.recv().unwrap(), 6);
-}
-
-#[test]
-fn test_recv_iter_break() {
-    let (tx, rx) = channel::<i32>();
-    let (count_tx, count_rx) = channel();
-
-    let _t = thread::spawn(move || {
-        let mut count = 0;
-        for x in rx.iter() {
-            if count >= 3 {
-                break;
-            } else {
-                count += x;
-            }
-        }
-        count_tx.send(count).unwrap();
-    });
-
-    tx.send(2).unwrap();
-    tx.send(2).unwrap();
-    tx.send(2).unwrap();
-    let _ = tx.send(2);
-    drop(tx);
-    assert_eq!(count_rx.recv().unwrap(), 4);
-}
-
-#[test]
-fn test_recv_try_iter() {
-    let (request_tx, request_rx) = channel();
-    let (response_tx, response_rx) = channel();
-
-    // Request `x`s until we have `6`.
-    let t = thread::spawn(move || {
-        let mut count = 0;
-        loop {
-            for x in response_rx.try_iter() {
-                count += x;
-                if count == 6 {
-                    return count;
-                }
-            }
-            request_tx.send(()).unwrap();
-        }
-    });
-
-    for _ in request_rx.iter() {
-        if response_tx.send(2).is_err() {
-            break;
-        }
-    }
-
-    assert_eq!(t.join().unwrap(), 6);
-}
-
-#[test]
-fn test_recv_into_iter_owned() {
-    let mut iter = {
-        let (tx, rx) = channel::<i32>();
-        tx.send(1).unwrap();
-        tx.send(2).unwrap();
-
-        rx.into_iter()
-    };
-    assert_eq!(iter.next().unwrap(), 1);
-    assert_eq!(iter.next().unwrap(), 2);
-    assert_eq!(iter.next().is_none(), true);
-}
-
-#[test]
-fn test_recv_into_iter_borrowed() {
-    let (tx, rx) = channel::<i32>();
-    tx.send(1).unwrap();
-    tx.send(2).unwrap();
-    drop(tx);
-    let mut iter = (&rx).into_iter();
-    assert_eq!(iter.next().unwrap(), 1);
-    assert_eq!(iter.next().unwrap(), 2);
-    assert_eq!(iter.next().is_none(), true);
-}
-
-#[test]
-fn try_recv_states() {
-    let (tx1, rx1) = channel::<i32>();
-    let (tx2, rx2) = channel::<()>();
-    let (tx3, rx3) = channel::<()>();
-    let _t = thread::spawn(move || {
-        rx2.recv().unwrap();
-        tx1.send(1).unwrap();
-        tx3.send(()).unwrap();
-        rx2.recv().unwrap();
-        drop(tx1);
-        tx3.send(()).unwrap();
-    });
-
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Empty));
-    tx2.send(()).unwrap();
-    rx3.recv().unwrap();
-    assert_eq!(rx1.try_recv(), Ok(1));
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Empty));
-    tx2.send(()).unwrap();
-    rx3.recv().unwrap();
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Disconnected));
-}
-
-// This bug used to end up in a livelock inside of the Receiver destructor
-// because the internal state of the Shared packet was corrupted
-#[test]
-fn destroy_upgraded_shared_port_when_sender_still_active() {
-    let (tx, rx) = channel();
-    let (tx2, rx2) = channel();
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap(); // wait on a oneshot
-        drop(rx); // destroy a shared
-        tx2.send(()).unwrap();
-    });
-    // make sure the other thread has gone to sleep
-    for _ in 0..5000 {
-        thread::yield_now();
-    }
-
-    // upgrade to a shared chan and send a message
-    let t = tx.clone();
-    drop(tx);
-    t.send(()).unwrap();
-
-    // wait for the child thread to exit before we exit
-    rx2.recv().unwrap();
-}
-
-#[test]
-fn issue_32114() {
-    let (tx, _) = channel();
-    let _ = tx.send(123);
-    assert_eq!(tx.send(123), Err(SendError(123)));
-}
-
-#[test]
-fn issue_39364() {
-    let (tx, rx) = channel::<()>();
-    let t = thread::spawn(move || {
-        thread::sleep(Duration::from_millis(300));
-        let _ = tx.clone();
-        // Don't drop; hand back to caller.
-        tx
-    });
-
-    let _ = rx.recv_timeout(Duration::from_millis(500));
-    let _tx = t.join().unwrap(); // delay dropping until end of test
-    let _ = rx.recv_timeout(Duration::from_millis(500));
-}
diff --git a/library/std/src/sync/mpsc/mod.rs b/library/std/src/sync/mpsc.rs
index c86b546e011..f942937c14d 100644
--- a/library/std/src/sync/mpsc/mod.rs
+++ b/library/std/src/sync/mpsc.rs
@@ -137,12 +137,6 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod sync_tests;
-
 // MPSC channels are built as a wrapper around MPMC channels, which
 // were ported from the `crossbeam-channel` crate. MPMC channels are
 // not exposed publicly, but if you are curious about the implementation,
@@ -737,9 +731,10 @@ impl<T> SyncSender<T> {
     // Attempts to send for a value on this receiver, returning an error if the
     // corresponding channel has hung up, or if it waits more than `timeout`.
     //
-    // This method is currently private and only used for tests.
-    #[allow(unused)]
-    fn send_timeout(&self, t: T, timeout: Duration) -> Result<(), mpmc::SendTimeoutError<T>> {
+    // This method is currently only used for tests.
+    #[unstable(issue = "none", feature = "std_internals")]
+    #[doc(hidden)]
+    pub fn send_timeout(&self, t: T, timeout: Duration) -> Result<(), mpmc::SendTimeoutError<T>> {
         self.inner.send_timeout(t, timeout)
     }
 }
diff --git a/library/std/src/sync/mpsc/sync_tests.rs b/library/std/src/sync/mpsc/sync_tests.rs
deleted file mode 100644
index 49b65c8efe6..00000000000
--- a/library/std/src/sync/mpsc/sync_tests.rs
+++ /dev/null
@@ -1,669 +0,0 @@
-use super::*;
-use crate::rc::Rc;
-use crate::sync::mpmc::SendTimeoutError;
-use crate::{env, thread};
-
-pub fn stress_factor() -> usize {
-    match env::var("RUST_TEST_STRESS") {
-        Ok(val) => val.parse().unwrap(),
-        Err(..) => 1,
-    }
-}
-
-#[test]
-fn smoke() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-}
-
-#[test]
-fn drop_full() {
-    let (tx, _rx) = sync_channel::<Box<isize>>(1);
-    tx.send(Box::new(1)).unwrap();
-}
-
-#[test]
-fn smoke_shared() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-    let tx = tx.clone();
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-}
-
-#[test]
-fn recv_timeout() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Err(RecvTimeoutError::Timeout));
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Ok(1));
-}
-
-#[test]
-fn send_timeout() {
-    let (tx, _rx) = sync_channel::<i32>(1);
-    assert_eq!(tx.send_timeout(1, Duration::from_millis(1)), Ok(()));
-    assert_eq!(tx.send_timeout(1, Duration::from_millis(1)), Err(SendTimeoutError::Timeout(1)));
-}
-
-#[test]
-fn smoke_threads() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    let _t = thread::spawn(move || {
-        tx.send(1).unwrap();
-    });
-    assert_eq!(rx.recv().unwrap(), 1);
-}
-
-#[test]
-fn smoke_port_gone() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    drop(rx);
-    assert!(tx.send(1).is_err());
-}
-
-#[test]
-fn smoke_shared_port_gone2() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    drop(rx);
-    let tx2 = tx.clone();
-    drop(tx);
-    assert!(tx2.send(1).is_err());
-}
-
-#[test]
-fn port_gone_concurrent() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap();
-    });
-    while tx.send(1).is_ok() {}
-}
-
-#[test]
-fn port_gone_concurrent_shared() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    let tx2 = tx.clone();
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap();
-    });
-    while tx.send(1).is_ok() && tx2.send(1).is_ok() {}
-}
-
-#[test]
-fn smoke_chan_gone() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    drop(tx);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn smoke_chan_gone_shared() {
-    let (tx, rx) = sync_channel::<()>(0);
-    let tx2 = tx.clone();
-    drop(tx);
-    drop(tx2);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn chan_gone_concurrent() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    thread::spawn(move || {
-        tx.send(1).unwrap();
-        tx.send(1).unwrap();
-    });
-    while rx.recv().is_ok() {}
-}
-
-#[test]
-fn stress() {
-    let count = if cfg!(miri) { 100 } else { 10000 };
-    let (tx, rx) = sync_channel::<i32>(0);
-    thread::spawn(move || {
-        for _ in 0..count {
-            tx.send(1).unwrap();
-        }
-    });
-    for _ in 0..count {
-        assert_eq!(rx.recv().unwrap(), 1);
-    }
-}
-
-#[test]
-fn stress_recv_timeout_two_threads() {
-    let count = if cfg!(miri) { 100 } else { 10000 };
-    let (tx, rx) = sync_channel::<i32>(0);
-
-    thread::spawn(move || {
-        for _ in 0..count {
-            tx.send(1).unwrap();
-        }
-    });
-
-    let mut recv_count = 0;
-    loop {
-        match rx.recv_timeout(Duration::from_millis(1)) {
-            Ok(v) => {
-                assert_eq!(v, 1);
-                recv_count += 1;
-            }
-            Err(RecvTimeoutError::Timeout) => continue,
-            Err(RecvTimeoutError::Disconnected) => break,
-        }
-    }
-
-    assert_eq!(recv_count, count);
-}
-
-#[test]
-fn stress_recv_timeout_shared() {
-    const AMT: u32 = if cfg!(miri) { 100 } else { 1000 };
-    const NTHREADS: u32 = 8;
-    let (tx, rx) = sync_channel::<i32>(0);
-    let (dtx, drx) = sync_channel::<()>(0);
-
-    thread::spawn(move || {
-        let mut recv_count = 0;
-        loop {
-            match rx.recv_timeout(Duration::from_millis(10)) {
-                Ok(v) => {
-                    assert_eq!(v, 1);
-                    recv_count += 1;
-                }
-                Err(RecvTimeoutError::Timeout) => continue,
-                Err(RecvTimeoutError::Disconnected) => break,
-            }
-        }
-
-        assert_eq!(recv_count, AMT * NTHREADS);
-        assert!(rx.try_recv().is_err());
-
-        dtx.send(()).unwrap();
-    });
-
-    for _ in 0..NTHREADS {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            for _ in 0..AMT {
-                tx.send(1).unwrap();
-            }
-        });
-    }
-
-    drop(tx);
-
-    drx.recv().unwrap();
-}
-
-#[test]
-fn stress_shared() {
-    const AMT: u32 = if cfg!(miri) { 100 } else { 1000 };
-    const NTHREADS: u32 = 8;
-    let (tx, rx) = sync_channel::<i32>(0);
-    let (dtx, drx) = sync_channel::<()>(0);
-
-    thread::spawn(move || {
-        for _ in 0..AMT * NTHREADS {
-            assert_eq!(rx.recv().unwrap(), 1);
-        }
-        match rx.try_recv() {
-            Ok(..) => panic!(),
-            _ => {}
-        }
-        dtx.send(()).unwrap();
-    });
-
-    for _ in 0..NTHREADS {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            for _ in 0..AMT {
-                tx.send(1).unwrap();
-            }
-        });
-    }
-    drop(tx);
-    drx.recv().unwrap();
-}
-
-#[test]
-fn oneshot_single_thread_close_port_first() {
-    // Simple test of closing without sending
-    let (_tx, rx) = sync_channel::<i32>(0);
-    drop(rx);
-}
-
-#[test]
-fn oneshot_single_thread_close_chan_first() {
-    // Simple test of closing without sending
-    let (tx, _rx) = sync_channel::<i32>(0);
-    drop(tx);
-}
-
-#[test]
-fn oneshot_single_thread_send_port_close() {
-    // Testing that the sender cleans up the payload if receiver is closed
-    let (tx, rx) = sync_channel::<Box<i32>>(0);
-    drop(rx);
-    assert!(tx.send(Box::new(0)).is_err());
-}
-
-#[test]
-fn oneshot_single_thread_recv_chan_close() {
-    // Receiving on a closed chan will panic
-    let res = thread::spawn(move || {
-        let (tx, rx) = sync_channel::<i32>(0);
-        drop(tx);
-        rx.recv().unwrap();
-    })
-    .join();
-    // What is our res?
-    assert!(res.is_err());
-}
-
-#[test]
-fn oneshot_single_thread_send_then_recv() {
-    let (tx, rx) = sync_channel::<Box<i32>>(1);
-    tx.send(Box::new(10)).unwrap();
-    assert!(*rx.recv().unwrap() == 10);
-}
-
-#[test]
-fn oneshot_single_thread_try_send_open() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    assert_eq!(tx.try_send(10), Ok(()));
-    assert!(rx.recv().unwrap() == 10);
-}
-
-#[test]
-fn oneshot_single_thread_try_send_closed() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    drop(rx);
-    assert_eq!(tx.try_send(10), Err(TrySendError::Disconnected(10)));
-}
-
-#[test]
-fn oneshot_single_thread_try_send_closed2() {
-    let (tx, _rx) = sync_channel::<i32>(0);
-    assert_eq!(tx.try_send(10), Err(TrySendError::Full(10)));
-}
-
-#[test]
-fn oneshot_single_thread_try_recv_open() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    tx.send(10).unwrap();
-    assert!(rx.recv() == Ok(10));
-}
-
-#[test]
-fn oneshot_single_thread_try_recv_closed() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    drop(tx);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn oneshot_single_thread_try_recv_closed_with_data() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    tx.send(10).unwrap();
-    drop(tx);
-    assert_eq!(rx.try_recv(), Ok(10));
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Disconnected));
-}
-
-#[test]
-fn oneshot_single_thread_peek_data() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Empty));
-    tx.send(10).unwrap();
-    assert_eq!(rx.try_recv(), Ok(10));
-}
-
-#[test]
-fn oneshot_single_thread_peek_close() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    drop(tx);
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Disconnected));
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Disconnected));
-}
-
-#[test]
-fn oneshot_single_thread_peek_open() {
-    let (_tx, rx) = sync_channel::<i32>(0);
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Empty));
-}
-
-#[test]
-fn oneshot_multi_task_recv_then_send() {
-    let (tx, rx) = sync_channel::<Box<i32>>(0);
-    let _t = thread::spawn(move || {
-        assert!(*rx.recv().unwrap() == 10);
-    });
-
-    tx.send(Box::new(10)).unwrap();
-}
-
-#[test]
-fn oneshot_multi_task_recv_then_close() {
-    let (tx, rx) = sync_channel::<Box<i32>>(0);
-    let _t = thread::spawn(move || {
-        drop(tx);
-    });
-    let res = thread::spawn(move || {
-        assert!(*rx.recv().unwrap() == 10);
-    })
-    .join();
-    assert!(res.is_err());
-}
-
-#[test]
-fn oneshot_multi_thread_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = sync_channel::<i32>(0);
-        let _t = thread::spawn(move || {
-            drop(rx);
-        });
-        drop(tx);
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_send_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = sync_channel::<i32>(0);
-        let _t = thread::spawn(move || {
-            drop(rx);
-        });
-        let _ = thread::spawn(move || {
-            tx.send(1).unwrap();
-        })
-        .join();
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_recv_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = sync_channel::<i32>(0);
-        let _t = thread::spawn(move || {
-            let res = thread::spawn(move || {
-                rx.recv().unwrap();
-            })
-            .join();
-            assert!(res.is_err());
-        });
-        let _t = thread::spawn(move || {
-            thread::spawn(move || {
-                drop(tx);
-            });
-        });
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_send_recv_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = sync_channel::<Box<i32>>(0);
-        let _t = thread::spawn(move || {
-            tx.send(Box::new(10)).unwrap();
-        });
-        assert!(*rx.recv().unwrap() == 10);
-    }
-}
-
-#[test]
-fn stream_send_recv_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = sync_channel::<Box<i32>>(0);
-
-        send(tx, 0);
-        recv(rx, 0);
-
-        fn send(tx: SyncSender<Box<i32>>, i: i32) {
-            if i == 10 {
-                return;
-            }
-
-            thread::spawn(move || {
-                tx.send(Box::new(i)).unwrap();
-                send(tx, i + 1);
-            });
-        }
-
-        fn recv(rx: Receiver<Box<i32>>, i: i32) {
-            if i == 10 {
-                return;
-            }
-
-            thread::spawn(move || {
-                assert!(*rx.recv().unwrap() == i);
-                recv(rx, i + 1);
-            });
-        }
-    }
-}
-
-#[test]
-fn recv_a_lot() {
-    let count = if cfg!(miri) { 1000 } else { 10000 };
-    // Regression test that we don't run out of stack in scheduler context
-    let (tx, rx) = sync_channel(count);
-    for _ in 0..count {
-        tx.send(()).unwrap();
-    }
-    for _ in 0..count {
-        rx.recv().unwrap();
-    }
-}
-
-#[test]
-fn shared_chan_stress() {
-    let (tx, rx) = sync_channel(0);
-    let total = stress_factor() + 100;
-    for _ in 0..total {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            tx.send(()).unwrap();
-        });
-    }
-
-    for _ in 0..total {
-        rx.recv().unwrap();
-    }
-}
-
-#[test]
-fn test_nested_recv_iter() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    let (total_tx, total_rx) = sync_channel::<i32>(0);
-
-    let _t = thread::spawn(move || {
-        let mut acc = 0;
-        for x in rx.iter() {
-            acc += x;
-        }
-        total_tx.send(acc).unwrap();
-    });
-
-    tx.send(3).unwrap();
-    tx.send(1).unwrap();
-    tx.send(2).unwrap();
-    drop(tx);
-    assert_eq!(total_rx.recv().unwrap(), 6);
-}
-
-#[test]
-fn test_recv_iter_break() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    let (count_tx, count_rx) = sync_channel(0);
-
-    let _t = thread::spawn(move || {
-        let mut count = 0;
-        for x in rx.iter() {
-            if count >= 3 {
-                break;
-            } else {
-                count += x;
-            }
-        }
-        count_tx.send(count).unwrap();
-    });
-
-    tx.send(2).unwrap();
-    tx.send(2).unwrap();
-    tx.send(2).unwrap();
-    let _ = tx.try_send(2);
-    drop(tx);
-    assert_eq!(count_rx.recv().unwrap(), 4);
-}
-
-#[test]
-fn try_recv_states() {
-    let (tx1, rx1) = sync_channel::<i32>(1);
-    let (tx2, rx2) = sync_channel::<()>(1);
-    let (tx3, rx3) = sync_channel::<()>(1);
-    let _t = thread::spawn(move || {
-        rx2.recv().unwrap();
-        tx1.send(1).unwrap();
-        tx3.send(()).unwrap();
-        rx2.recv().unwrap();
-        drop(tx1);
-        tx3.send(()).unwrap();
-    });
-
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Empty));
-    tx2.send(()).unwrap();
-    rx3.recv().unwrap();
-    assert_eq!(rx1.try_recv(), Ok(1));
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Empty));
-    tx2.send(()).unwrap();
-    rx3.recv().unwrap();
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Disconnected));
-}
-
-// This bug used to end up in a livelock inside of the Receiver destructor
-// because the internal state of the Shared packet was corrupted
-#[test]
-fn destroy_upgraded_shared_port_when_sender_still_active() {
-    let (tx, rx) = sync_channel::<()>(0);
-    let (tx2, rx2) = sync_channel::<()>(0);
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap(); // wait on a oneshot
-        drop(rx); // destroy a shared
-        tx2.send(()).unwrap();
-    });
-    // make sure the other thread has gone to sleep
-    for _ in 0..5000 {
-        thread::yield_now();
-    }
-
-    // upgrade to a shared chan and send a message
-    let t = tx.clone();
-    drop(tx);
-    t.send(()).unwrap();
-
-    // wait for the child thread to exit before we exit
-    rx2.recv().unwrap();
-}
-
-#[test]
-fn send1() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap();
-    });
-    assert_eq!(tx.send(1), Ok(()));
-}
-
-#[test]
-fn send2() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    let _t = thread::spawn(move || {
-        drop(rx);
-    });
-    assert!(tx.send(1).is_err());
-}
-
-#[test]
-fn send3() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    assert_eq!(tx.send(1), Ok(()));
-    let _t = thread::spawn(move || {
-        drop(rx);
-    });
-    assert!(tx.send(1).is_err());
-}
-
-#[test]
-fn send4() {
-    let (tx, rx) = sync_channel::<i32>(0);
-    let tx2 = tx.clone();
-    let (done, donerx) = channel();
-    let done2 = done.clone();
-    let _t = thread::spawn(move || {
-        assert!(tx.send(1).is_err());
-        done.send(()).unwrap();
-    });
-    let _t = thread::spawn(move || {
-        assert!(tx2.send(2).is_err());
-        done2.send(()).unwrap();
-    });
-    drop(rx);
-    donerx.recv().unwrap();
-    donerx.recv().unwrap();
-}
-
-#[test]
-fn try_send1() {
-    let (tx, _rx) = sync_channel::<i32>(0);
-    assert_eq!(tx.try_send(1), Err(TrySendError::Full(1)));
-}
-
-#[test]
-fn try_send2() {
-    let (tx, _rx) = sync_channel::<i32>(1);
-    assert_eq!(tx.try_send(1), Ok(()));
-    assert_eq!(tx.try_send(1), Err(TrySendError::Full(1)));
-}
-
-#[test]
-fn try_send3() {
-    let (tx, rx) = sync_channel::<i32>(1);
-    assert_eq!(tx.try_send(1), Ok(()));
-    drop(rx);
-    assert_eq!(tx.try_send(1), Err(TrySendError::Disconnected(1)));
-}
-
-#[test]
-fn issue_15761() {
-    fn repro() {
-        let (tx1, rx1) = sync_channel::<()>(3);
-        let (tx2, rx2) = sync_channel::<()>(3);
-
-        let _t = thread::spawn(move || {
-            rx1.recv().unwrap();
-            tx2.try_send(()).unwrap();
-        });
-
-        tx1.try_send(()).unwrap();
-        rx2.recv().unwrap();
-    }
-
-    for _ in 0..100 {
-        repro()
-    }
-}
-
-#[test]
-fn drop_unreceived() {
-    let (tx, rx) = sync_channel::<Rc<()>>(1);
-    let msg = Rc::new(());
-    let weak = Rc::downgrade(&msg);
-    assert!(tx.send(msg).is_ok());
-    drop(rx);
-    // Messages should be dropped immediately when the last receiver is destroyed.
-    assert!(weak.upgrade().is_none());
-    drop(tx);
-}
diff --git a/library/std/src/sync/mpsc/tests.rs b/library/std/src/sync/mpsc/tests.rs
deleted file mode 100644
index 13892fa0d18..00000000000
--- a/library/std/src/sync/mpsc/tests.rs
+++ /dev/null
@@ -1,721 +0,0 @@
-use super::*;
-use crate::{env, thread};
-
-pub fn stress_factor() -> usize {
-    match env::var("RUST_TEST_STRESS") {
-        Ok(val) => val.parse().unwrap(),
-        Err(..) => 1,
-    }
-}
-
-#[test]
-fn smoke() {
-    let (tx, rx) = channel::<i32>();
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-}
-
-#[test]
-fn drop_full() {
-    let (tx, _rx) = channel::<Box<isize>>();
-    tx.send(Box::new(1)).unwrap();
-}
-
-#[test]
-fn drop_full_shared() {
-    let (tx, _rx) = channel::<Box<isize>>();
-    drop(tx.clone());
-    drop(tx.clone());
-    tx.send(Box::new(1)).unwrap();
-}
-
-#[test]
-fn smoke_shared() {
-    let (tx, rx) = channel::<i32>();
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-    let tx = tx.clone();
-    tx.send(1).unwrap();
-    assert_eq!(rx.recv().unwrap(), 1);
-}
-
-#[test]
-fn smoke_threads() {
-    let (tx, rx) = channel::<i32>();
-    let _t = thread::spawn(move || {
-        tx.send(1).unwrap();
-    });
-    assert_eq!(rx.recv().unwrap(), 1);
-}
-
-#[test]
-fn smoke_port_gone() {
-    let (tx, rx) = channel::<i32>();
-    drop(rx);
-    assert!(tx.send(1).is_err());
-}
-
-#[test]
-fn smoke_shared_port_gone() {
-    let (tx, rx) = channel::<i32>();
-    drop(rx);
-    assert!(tx.send(1).is_err())
-}
-
-#[test]
-fn smoke_shared_port_gone2() {
-    let (tx, rx) = channel::<i32>();
-    drop(rx);
-    let tx2 = tx.clone();
-    drop(tx);
-    assert!(tx2.send(1).is_err());
-}
-
-#[test]
-fn port_gone_concurrent() {
-    let (tx, rx) = channel::<i32>();
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap();
-    });
-    while tx.send(1).is_ok() {}
-}
-
-#[test]
-fn port_gone_concurrent_shared() {
-    let (tx, rx) = channel::<i32>();
-    let tx2 = tx.clone();
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap();
-    });
-    while tx.send(1).is_ok() && tx2.send(1).is_ok() {}
-}
-
-#[test]
-fn smoke_chan_gone() {
-    let (tx, rx) = channel::<i32>();
-    drop(tx);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn smoke_chan_gone_shared() {
-    let (tx, rx) = channel::<()>();
-    let tx2 = tx.clone();
-    drop(tx);
-    drop(tx2);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn chan_gone_concurrent() {
-    let (tx, rx) = channel::<i32>();
-    let _t = thread::spawn(move || {
-        tx.send(1).unwrap();
-        tx.send(1).unwrap();
-    });
-    while rx.recv().is_ok() {}
-}
-
-#[test]
-fn stress() {
-    let count = if cfg!(miri) { 100 } else { 10000 };
-    let (tx, rx) = channel::<i32>();
-    let t = thread::spawn(move || {
-        for _ in 0..count {
-            tx.send(1).unwrap();
-        }
-    });
-    for _ in 0..count {
-        assert_eq!(rx.recv().unwrap(), 1);
-    }
-    t.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn stress_shared() {
-    const AMT: u32 = if cfg!(miri) { 100 } else { 10000 };
-    const NTHREADS: u32 = 8;
-    let (tx, rx) = channel::<i32>();
-
-    let t = thread::spawn(move || {
-        for _ in 0..AMT * NTHREADS {
-            assert_eq!(rx.recv().unwrap(), 1);
-        }
-        match rx.try_recv() {
-            Ok(..) => panic!(),
-            _ => {}
-        }
-    });
-
-    for _ in 0..NTHREADS {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            for _ in 0..AMT {
-                tx.send(1).unwrap();
-            }
-        });
-    }
-    drop(tx);
-    t.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn send_from_outside_runtime() {
-    let (tx1, rx1) = channel::<()>();
-    let (tx2, rx2) = channel::<i32>();
-    let t1 = thread::spawn(move || {
-        tx1.send(()).unwrap();
-        for _ in 0..40 {
-            assert_eq!(rx2.recv().unwrap(), 1);
-        }
-    });
-    rx1.recv().unwrap();
-    let t2 = thread::spawn(move || {
-        for _ in 0..40 {
-            tx2.send(1).unwrap();
-        }
-    });
-    t1.join().ok().expect("thread panicked");
-    t2.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn recv_from_outside_runtime() {
-    let (tx, rx) = channel::<i32>();
-    let t = thread::spawn(move || {
-        for _ in 0..40 {
-            assert_eq!(rx.recv().unwrap(), 1);
-        }
-    });
-    for _ in 0..40 {
-        tx.send(1).unwrap();
-    }
-    t.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn no_runtime() {
-    let (tx1, rx1) = channel::<i32>();
-    let (tx2, rx2) = channel::<i32>();
-    let t1 = thread::spawn(move || {
-        assert_eq!(rx1.recv().unwrap(), 1);
-        tx2.send(2).unwrap();
-    });
-    let t2 = thread::spawn(move || {
-        tx1.send(1).unwrap();
-        assert_eq!(rx2.recv().unwrap(), 2);
-    });
-    t1.join().ok().expect("thread panicked");
-    t2.join().ok().expect("thread panicked");
-}
-
-#[test]
-fn oneshot_single_thread_close_port_first() {
-    // Simple test of closing without sending
-    let (_tx, rx) = channel::<i32>();
-    drop(rx);
-}
-
-#[test]
-fn oneshot_single_thread_close_chan_first() {
-    // Simple test of closing without sending
-    let (tx, _rx) = channel::<i32>();
-    drop(tx);
-}
-
-#[test]
-fn oneshot_single_thread_send_port_close() {
-    // Testing that the sender cleans up the payload if receiver is closed
-    let (tx, rx) = channel::<Box<i32>>();
-    drop(rx);
-    assert!(tx.send(Box::new(0)).is_err());
-}
-
-#[test]
-fn oneshot_single_thread_recv_chan_close() {
-    // Receiving on a closed chan will panic
-    let res = thread::spawn(move || {
-        let (tx, rx) = channel::<i32>();
-        drop(tx);
-        rx.recv().unwrap();
-    })
-    .join();
-    // What is our res?
-    assert!(res.is_err());
-}
-
-#[test]
-fn oneshot_single_thread_send_then_recv() {
-    let (tx, rx) = channel::<Box<i32>>();
-    tx.send(Box::new(10)).unwrap();
-    assert!(*rx.recv().unwrap() == 10);
-}
-
-#[test]
-fn oneshot_single_thread_try_send_open() {
-    let (tx, rx) = channel::<i32>();
-    assert!(tx.send(10).is_ok());
-    assert!(rx.recv().unwrap() == 10);
-}
-
-#[test]
-fn oneshot_single_thread_try_send_closed() {
-    let (tx, rx) = channel::<i32>();
-    drop(rx);
-    assert!(tx.send(10).is_err());
-}
-
-#[test]
-fn oneshot_single_thread_try_recv_open() {
-    let (tx, rx) = channel::<i32>();
-    tx.send(10).unwrap();
-    assert!(rx.recv() == Ok(10));
-}
-
-#[test]
-fn oneshot_single_thread_try_recv_closed() {
-    let (tx, rx) = channel::<i32>();
-    drop(tx);
-    assert!(rx.recv().is_err());
-}
-
-#[test]
-fn oneshot_single_thread_peek_data() {
-    let (tx, rx) = channel::<i32>();
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Empty));
-    tx.send(10).unwrap();
-    assert_eq!(rx.try_recv(), Ok(10));
-}
-
-#[test]
-fn oneshot_single_thread_peek_close() {
-    let (tx, rx) = channel::<i32>();
-    drop(tx);
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Disconnected));
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Disconnected));
-}
-
-#[test]
-fn oneshot_single_thread_peek_open() {
-    let (_tx, rx) = channel::<i32>();
-    assert_eq!(rx.try_recv(), Err(TryRecvError::Empty));
-}
-
-#[test]
-fn oneshot_multi_task_recv_then_send() {
-    let (tx, rx) = channel::<Box<i32>>();
-    let _t = thread::spawn(move || {
-        assert!(*rx.recv().unwrap() == 10);
-    });
-
-    tx.send(Box::new(10)).unwrap();
-}
-
-#[test]
-fn oneshot_multi_task_recv_then_close() {
-    let (tx, rx) = channel::<Box<i32>>();
-    let _t = thread::spawn(move || {
-        drop(tx);
-    });
-    let res = thread::spawn(move || {
-        assert!(*rx.recv().unwrap() == 10);
-    })
-    .join();
-    assert!(res.is_err());
-}
-
-#[test]
-fn oneshot_multi_thread_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel::<i32>();
-        let _t = thread::spawn(move || {
-            drop(rx);
-        });
-        drop(tx);
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_send_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel::<i32>();
-        let _t = thread::spawn(move || {
-            drop(rx);
-        });
-        let _ = thread::spawn(move || {
-            tx.send(1).unwrap();
-        })
-        .join();
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_recv_close_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel::<i32>();
-        thread::spawn(move || {
-            let res = thread::spawn(move || {
-                rx.recv().unwrap();
-            })
-            .join();
-            assert!(res.is_err());
-        });
-        let _t = thread::spawn(move || {
-            thread::spawn(move || {
-                drop(tx);
-            });
-        });
-    }
-}
-
-#[test]
-fn oneshot_multi_thread_send_recv_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel::<Box<isize>>();
-        let _t = thread::spawn(move || {
-            tx.send(Box::new(10)).unwrap();
-        });
-        assert!(*rx.recv().unwrap() == 10);
-    }
-}
-
-#[test]
-fn stream_send_recv_stress() {
-    for _ in 0..stress_factor() {
-        let (tx, rx) = channel();
-
-        send(tx, 0);
-        recv(rx, 0);
-
-        fn send(tx: Sender<Box<i32>>, i: i32) {
-            if i == 10 {
-                return;
-            }
-
-            thread::spawn(move || {
-                tx.send(Box::new(i)).unwrap();
-                send(tx, i + 1);
-            });
-        }
-
-        fn recv(rx: Receiver<Box<i32>>, i: i32) {
-            if i == 10 {
-                return;
-            }
-
-            thread::spawn(move || {
-                assert!(*rx.recv().unwrap() == i);
-                recv(rx, i + 1);
-            });
-        }
-    }
-}
-
-#[test]
-fn oneshot_single_thread_recv_timeout() {
-    let (tx, rx) = channel();
-    tx.send(()).unwrap();
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Ok(()));
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Err(RecvTimeoutError::Timeout));
-    tx.send(()).unwrap();
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Ok(()));
-}
-
-#[test]
-fn stress_recv_timeout_two_threads() {
-    let (tx, rx) = channel();
-    let stress = stress_factor() + 100;
-    let timeout = Duration::from_millis(100);
-
-    thread::spawn(move || {
-        for i in 0..stress {
-            if i % 2 == 0 {
-                thread::sleep(timeout * 2);
-            }
-            tx.send(1usize).unwrap();
-        }
-    });
-
-    let mut recv_count = 0;
-    loop {
-        match rx.recv_timeout(timeout) {
-            Ok(n) => {
-                assert_eq!(n, 1usize);
-                recv_count += 1;
-            }
-            Err(RecvTimeoutError::Timeout) => continue,
-            Err(RecvTimeoutError::Disconnected) => break,
-        }
-    }
-
-    assert_eq!(recv_count, stress);
-}
-
-#[test]
-fn recv_timeout_upgrade() {
-    let (tx, rx) = channel::<()>();
-    let timeout = Duration::from_millis(1);
-    let _tx_clone = tx.clone();
-
-    let start = Instant::now();
-    assert_eq!(rx.recv_timeout(timeout), Err(RecvTimeoutError::Timeout));
-    assert!(Instant::now() >= start + timeout);
-}
-
-#[test]
-fn stress_recv_timeout_shared() {
-    let (tx, rx) = channel();
-    let stress = stress_factor() + 100;
-
-    for i in 0..stress {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            thread::sleep(Duration::from_millis(i as u64 * 10));
-            tx.send(1usize).unwrap();
-        });
-    }
-
-    drop(tx);
-
-    let mut recv_count = 0;
-    loop {
-        match rx.recv_timeout(Duration::from_millis(10)) {
-            Ok(n) => {
-                assert_eq!(n, 1usize);
-                recv_count += 1;
-            }
-            Err(RecvTimeoutError::Timeout) => continue,
-            Err(RecvTimeoutError::Disconnected) => break,
-        }
-    }
-
-    assert_eq!(recv_count, stress);
-}
-
-#[test]
-fn very_long_recv_timeout_wont_panic() {
-    let (tx, rx) = channel::<()>();
-    let join_handle = thread::spawn(move || rx.recv_timeout(Duration::from_secs(u64::MAX)));
-    thread::sleep(Duration::from_secs(1));
-    assert!(tx.send(()).is_ok());
-    assert_eq!(join_handle.join().unwrap(), Ok(()));
-}
-
-#[test]
-fn recv_a_lot() {
-    let count = if cfg!(miri) { 1000 } else { 10000 };
-    // Regression test that we don't run out of stack in scheduler context
-    let (tx, rx) = channel();
-    for _ in 0..count {
-        tx.send(()).unwrap();
-    }
-    for _ in 0..count {
-        rx.recv().unwrap();
-    }
-}
-
-#[test]
-fn shared_recv_timeout() {
-    let (tx, rx) = channel();
-    let total = 5;
-    for _ in 0..total {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            tx.send(()).unwrap();
-        });
-    }
-
-    for _ in 0..total {
-        rx.recv().unwrap();
-    }
-
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Err(RecvTimeoutError::Timeout));
-    tx.send(()).unwrap();
-    assert_eq!(rx.recv_timeout(Duration::from_millis(1)), Ok(()));
-}
-
-#[test]
-fn shared_chan_stress() {
-    let (tx, rx) = channel();
-    let total = stress_factor() + 100;
-    for _ in 0..total {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            tx.send(()).unwrap();
-        });
-    }
-
-    for _ in 0..total {
-        rx.recv().unwrap();
-    }
-}
-
-#[test]
-fn test_nested_recv_iter() {
-    let (tx, rx) = channel::<i32>();
-    let (total_tx, total_rx) = channel::<i32>();
-
-    let _t = thread::spawn(move || {
-        let mut acc = 0;
-        for x in rx.iter() {
-            acc += x;
-        }
-        total_tx.send(acc).unwrap();
-    });
-
-    tx.send(3).unwrap();
-    tx.send(1).unwrap();
-    tx.send(2).unwrap();
-    drop(tx);
-    assert_eq!(total_rx.recv().unwrap(), 6);
-}
-
-#[test]
-fn test_recv_iter_break() {
-    let (tx, rx) = channel::<i32>();
-    let (count_tx, count_rx) = channel();
-
-    let _t = thread::spawn(move || {
-        let mut count = 0;
-        for x in rx.iter() {
-            if count >= 3 {
-                break;
-            } else {
-                count += x;
-            }
-        }
-        count_tx.send(count).unwrap();
-    });
-
-    tx.send(2).unwrap();
-    tx.send(2).unwrap();
-    tx.send(2).unwrap();
-    let _ = tx.send(2);
-    drop(tx);
-    assert_eq!(count_rx.recv().unwrap(), 4);
-}
-
-#[test]
-fn test_recv_try_iter() {
-    let (request_tx, request_rx) = channel();
-    let (response_tx, response_rx) = channel();
-
-    // Request `x`s until we have `6`.
-    let t = thread::spawn(move || {
-        let mut count = 0;
-        loop {
-            for x in response_rx.try_iter() {
-                count += x;
-                if count == 6 {
-                    return count;
-                }
-            }
-            request_tx.send(()).unwrap();
-        }
-    });
-
-    for _ in request_rx.iter() {
-        if response_tx.send(2).is_err() {
-            break;
-        }
-    }
-
-    assert_eq!(t.join().unwrap(), 6);
-}
-
-#[test]
-fn test_recv_into_iter_owned() {
-    let mut iter = {
-        let (tx, rx) = channel::<i32>();
-        tx.send(1).unwrap();
-        tx.send(2).unwrap();
-
-        rx.into_iter()
-    };
-    assert_eq!(iter.next().unwrap(), 1);
-    assert_eq!(iter.next().unwrap(), 2);
-    assert_eq!(iter.next().is_none(), true);
-}
-
-#[test]
-fn test_recv_into_iter_borrowed() {
-    let (tx, rx) = channel::<i32>();
-    tx.send(1).unwrap();
-    tx.send(2).unwrap();
-    drop(tx);
-    let mut iter = (&rx).into_iter();
-    assert_eq!(iter.next().unwrap(), 1);
-    assert_eq!(iter.next().unwrap(), 2);
-    assert_eq!(iter.next().is_none(), true);
-}
-
-#[test]
-fn try_recv_states() {
-    let (tx1, rx1) = channel::<i32>();
-    let (tx2, rx2) = channel::<()>();
-    let (tx3, rx3) = channel::<()>();
-    let _t = thread::spawn(move || {
-        rx2.recv().unwrap();
-        tx1.send(1).unwrap();
-        tx3.send(()).unwrap();
-        rx2.recv().unwrap();
-        drop(tx1);
-        tx3.send(()).unwrap();
-    });
-
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Empty));
-    tx2.send(()).unwrap();
-    rx3.recv().unwrap();
-    assert_eq!(rx1.try_recv(), Ok(1));
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Empty));
-    tx2.send(()).unwrap();
-    rx3.recv().unwrap();
-    assert_eq!(rx1.try_recv(), Err(TryRecvError::Disconnected));
-}
-
-// This bug used to end up in a livelock inside of the Receiver destructor
-// because the internal state of the Shared packet was corrupted
-#[test]
-fn destroy_upgraded_shared_port_when_sender_still_active() {
-    let (tx, rx) = channel();
-    let (tx2, rx2) = channel();
-    let _t = thread::spawn(move || {
-        rx.recv().unwrap(); // wait on a oneshot
-        drop(rx); // destroy a shared
-        tx2.send(()).unwrap();
-    });
-    // make sure the other thread has gone to sleep
-    for _ in 0..5000 {
-        thread::yield_now();
-    }
-
-    // upgrade to a shared chan and send a message
-    let t = tx.clone();
-    drop(tx);
-    t.send(()).unwrap();
-
-    // wait for the child thread to exit before we exit
-    rx2.recv().unwrap();
-}
-
-#[test]
-fn issue_32114() {
-    let (tx, _) = channel();
-    let _ = tx.send(123);
-    assert_eq!(tx.send(123), Err(SendError(123)));
-}
-
-#[test]
-fn issue_39364() {
-    let (tx, rx) = channel::<()>();
-    let t = thread::spawn(move || {
-        thread::sleep(Duration::from_millis(300));
-        let _ = tx.clone();
-        // Don't drop; hand back to caller.
-        tx
-    });
-
-    let _ = rx.recv_timeout(Duration::from_millis(500));
-    let _tx = t.join().unwrap(); // delay dropping until end of test
-    let _ = rx.recv_timeout(Duration::from_millis(500));
-}
diff --git a/library/std/src/sync/once_lock.rs b/library/std/src/sync/once_lock.rs
index 8f769f2dca3..21e6b65a744 100644
--- a/library/std/src/sync/once_lock.rs
+++ b/library/std/src/sync/once_lock.rs
@@ -681,6 +681,3 @@ unsafe impl<#[may_dangle] T> Drop for OnceLock<T> {
         }
     }
 }
-
-#[cfg(test)]
-mod tests;
diff --git a/library/std/src/sync/once_lock/tests.rs b/library/std/src/sync/once_lock/tests.rs
deleted file mode 100644
index 5113d436c3c..00000000000
--- a/library/std/src/sync/once_lock/tests.rs
+++ /dev/null
@@ -1,200 +0,0 @@
-use crate::sync::OnceLock;
-use crate::sync::atomic::AtomicUsize;
-use crate::sync::atomic::Ordering::SeqCst;
-use crate::sync::mpsc::channel;
-use crate::{panic, thread};
-
-fn spawn_and_wait<R: Send + 'static>(f: impl FnOnce() -> R + Send + 'static) -> R {
-    thread::spawn(f).join().unwrap()
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn sync_once_cell() {
-    static ONCE_CELL: OnceLock<i32> = OnceLock::new();
-
-    assert!(ONCE_CELL.get().is_none());
-
-    spawn_and_wait(|| {
-        ONCE_CELL.get_or_init(|| 92);
-        assert_eq!(ONCE_CELL.get(), Some(&92));
-    });
-
-    ONCE_CELL.get_or_init(|| panic!("Kaboom!"));
-    assert_eq!(ONCE_CELL.get(), Some(&92));
-}
-
-#[test]
-fn sync_once_cell_get_mut() {
-    let mut c = OnceLock::new();
-    assert!(c.get_mut().is_none());
-    c.set(90).unwrap();
-    *c.get_mut().unwrap() += 2;
-    assert_eq!(c.get_mut(), Some(&mut 92));
-}
-
-#[test]
-fn sync_once_cell_get_unchecked() {
-    let c = OnceLock::new();
-    c.set(92).unwrap();
-    unsafe {
-        assert_eq!(c.get_unchecked(), &92);
-    }
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn sync_once_cell_drop() {
-    static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
-    struct Dropper;
-    impl Drop for Dropper {
-        fn drop(&mut self) {
-            DROP_CNT.fetch_add(1, SeqCst);
-        }
-    }
-
-    let x = OnceLock::new();
-    spawn_and_wait(move || {
-        x.get_or_init(|| Dropper);
-        assert_eq!(DROP_CNT.load(SeqCst), 0);
-        drop(x);
-    });
-
-    assert_eq!(DROP_CNT.load(SeqCst), 1);
-}
-
-#[test]
-fn sync_once_cell_drop_empty() {
-    let x = OnceLock::<String>::new();
-    drop(x);
-}
-
-#[test]
-fn clone() {
-    let s = OnceLock::new();
-    let c = s.clone();
-    assert!(c.get().is_none());
-
-    s.set("hello".to_string()).unwrap();
-    let c = s.clone();
-    assert_eq!(c.get().map(String::as_str), Some("hello"));
-}
-
-#[test]
-#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn get_or_try_init() {
-    let cell: OnceLock<String> = OnceLock::new();
-    assert!(cell.get().is_none());
-
-    let res = panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
-    assert!(res.is_err());
-    assert!(!cell.is_initialized());
-    assert!(cell.get().is_none());
-
-    assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
-
-    assert_eq!(cell.get_or_try_init(|| Ok::<_, ()>("hello".to_string())), Ok(&"hello".to_string()));
-    assert_eq!(cell.get(), Some(&"hello".to_string()));
-}
-
-#[test]
-fn from_impl() {
-    assert_eq!(OnceLock::from("value").get(), Some(&"value"));
-    assert_ne!(OnceLock::from("foo").get(), Some(&"bar"));
-}
-
-#[test]
-fn partialeq_impl() {
-    assert!(OnceLock::from("value") == OnceLock::from("value"));
-    assert!(OnceLock::from("foo") != OnceLock::from("bar"));
-
-    assert!(OnceLock::<String>::new() == OnceLock::new());
-    assert!(OnceLock::<String>::new() != OnceLock::from("value".to_owned()));
-}
-
-#[test]
-fn into_inner() {
-    let cell: OnceLock<String> = OnceLock::new();
-    assert_eq!(cell.into_inner(), None);
-    let cell = OnceLock::new();
-    cell.set("hello".to_string()).unwrap();
-    assert_eq!(cell.into_inner(), Some("hello".to_string()));
-}
-
-#[test]
-fn is_sync_send() {
-    fn assert_traits<T: Send + Sync>() {}
-    assert_traits::<OnceLock<String>>();
-}
-
-#[test]
-fn eval_once_macro() {
-    macro_rules! eval_once {
-        (|| -> $ty:ty {
-            $($body:tt)*
-        }) => {{
-            static ONCE_CELL: OnceLock<$ty> = OnceLock::new();
-            fn init() -> $ty {
-                $($body)*
-            }
-            ONCE_CELL.get_or_init(init)
-        }};
-    }
-
-    let fib: &'static Vec<i32> = eval_once! {
-        || -> Vec<i32> {
-            let mut res = vec![1, 1];
-            for i in 0..10 {
-                let next = res[i] + res[i + 1];
-                res.push(next);
-            }
-            res
-        }
-    };
-    assert_eq!(fib[5], 8)
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn sync_once_cell_does_not_leak_partially_constructed_boxes() {
-    static ONCE_CELL: OnceLock<String> = OnceLock::new();
-
-    let n_readers = 10;
-    let n_writers = 3;
-    const MSG: &str = "Hello, World";
-
-    let (tx, rx) = channel();
-
-    for _ in 0..n_readers {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            loop {
-                if let Some(msg) = ONCE_CELL.get() {
-                    tx.send(msg).unwrap();
-                    break;
-                }
-                #[cfg(target_env = "sgx")]
-                crate::thread::yield_now();
-            }
-        });
-    }
-    for _ in 0..n_writers {
-        thread::spawn(move || {
-            let _ = ONCE_CELL.set(MSG.to_owned());
-        });
-    }
-
-    for _ in 0..n_readers {
-        let msg = rx.recv().unwrap();
-        assert_eq!(msg, MSG);
-    }
-}
-
-#[test]
-fn dropck() {
-    let cell = OnceLock::new();
-    {
-        let s = String::new();
-        cell.set(&s).unwrap();
-    }
-}
diff --git a/library/std/src/sync/poison/condvar.rs b/library/std/src/sync/poison/condvar.rs
index a6e2389c93b..7f0f3f652bc 100644
--- a/library/std/src/sync/poison/condvar.rs
+++ b/library/std/src/sync/poison/condvar.rs
@@ -1,6 +1,3 @@
-#[cfg(test)]
-mod tests;
-
 use crate::fmt;
 use crate::sync::poison::{self, LockResult, MutexGuard, PoisonError, mutex};
 use crate::sys::sync as sys;
diff --git a/library/std/src/sync/poison/condvar/tests.rs b/library/std/src/sync/poison/condvar/tests.rs
deleted file mode 100644
index f9e9066bc92..00000000000
--- a/library/std/src/sync/poison/condvar/tests.rs
+++ /dev/null
@@ -1,190 +0,0 @@
-use crate::sync::atomic::{AtomicBool, Ordering};
-use crate::sync::mpsc::channel;
-use crate::sync::{Arc, Condvar, Mutex};
-use crate::thread;
-use crate::time::Duration;
-
-#[test]
-fn smoke() {
-    let c = Condvar::new();
-    c.notify_one();
-    c.notify_all();
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn notify_one() {
-    let m = Arc::new(Mutex::new(()));
-    let m2 = m.clone();
-    let c = Arc::new(Condvar::new());
-    let c2 = c.clone();
-
-    let g = m.lock().unwrap();
-    let _t = thread::spawn(move || {
-        let _g = m2.lock().unwrap();
-        c2.notify_one();
-    });
-    let g = c.wait(g).unwrap();
-    drop(g);
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn notify_all() {
-    const N: usize = 10;
-
-    let data = Arc::new((Mutex::new(0), Condvar::new()));
-    let (tx, rx) = channel();
-    for _ in 0..N {
-        let data = data.clone();
-        let tx = tx.clone();
-        thread::spawn(move || {
-            let &(ref lock, ref cond) = &*data;
-            let mut cnt = lock.lock().unwrap();
-            *cnt += 1;
-            if *cnt == N {
-                tx.send(()).unwrap();
-            }
-            while *cnt != 0 {
-                cnt = cond.wait(cnt).unwrap();
-            }
-            tx.send(()).unwrap();
-        });
-    }
-    drop(tx);
-
-    let &(ref lock, ref cond) = &*data;
-    rx.recv().unwrap();
-    let mut cnt = lock.lock().unwrap();
-    *cnt = 0;
-    cond.notify_all();
-    drop(cnt);
-
-    for _ in 0..N {
-        rx.recv().unwrap();
-    }
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn wait_while() {
-    let pair = Arc::new((Mutex::new(false), Condvar::new()));
-    let pair2 = pair.clone();
-
-    // Inside of our lock, spawn a new thread, and then wait for it to start.
-    thread::spawn(move || {
-        let &(ref lock, ref cvar) = &*pair2;
-        let mut started = lock.lock().unwrap();
-        *started = true;
-        // We notify the condvar that the value has changed.
-        cvar.notify_one();
-    });
-
-    // Wait for the thread to start up.
-    let &(ref lock, ref cvar) = &*pair;
-    let guard = cvar.wait_while(lock.lock().unwrap(), |started| !*started);
-    assert!(*guard.unwrap());
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // condvar wait not supported
-fn wait_timeout_wait() {
-    let m = Arc::new(Mutex::new(()));
-    let c = Arc::new(Condvar::new());
-
-    loop {
-        let g = m.lock().unwrap();
-        let (_g, no_timeout) = c.wait_timeout(g, Duration::from_millis(1)).unwrap();
-        // spurious wakeups mean this isn't necessarily true
-        // so execute test again, if not timeout
-        if !no_timeout.timed_out() {
-            continue;
-        }
-
-        break;
-    }
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // condvar wait not supported
-fn wait_timeout_while_wait() {
-    let m = Arc::new(Mutex::new(()));
-    let c = Arc::new(Condvar::new());
-
-    let g = m.lock().unwrap();
-    let (_g, wait) = c.wait_timeout_while(g, Duration::from_millis(1), |_| true).unwrap();
-    // no spurious wakeups. ensure it timed-out
-    assert!(wait.timed_out());
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // condvar wait not supported
-fn wait_timeout_while_instant_satisfy() {
-    let m = Arc::new(Mutex::new(()));
-    let c = Arc::new(Condvar::new());
-
-    let g = m.lock().unwrap();
-    let (_g, wait) = c.wait_timeout_while(g, Duration::from_millis(0), |_| false).unwrap();
-    // ensure it didn't time-out even if we were not given any time.
-    assert!(!wait.timed_out());
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn wait_timeout_while_wake() {
-    let pair = Arc::new((Mutex::new(false), Condvar::new()));
-    let pair_copy = pair.clone();
-
-    let &(ref m, ref c) = &*pair;
-    let g = m.lock().unwrap();
-    let _t = thread::spawn(move || {
-        let &(ref lock, ref cvar) = &*pair_copy;
-        let mut started = lock.lock().unwrap();
-        thread::sleep(Duration::from_millis(1));
-        *started = true;
-        cvar.notify_one();
-    });
-    let (g2, wait) = c
-        .wait_timeout_while(g, Duration::from_millis(u64::MAX), |&mut notified| !notified)
-        .unwrap();
-    // ensure it didn't time-out even if we were not given any time.
-    assert!(!wait.timed_out());
-    assert!(*g2);
-}
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
-fn wait_timeout_wake() {
-    let m = Arc::new(Mutex::new(()));
-    let c = Arc::new(Condvar::new());
-
-    loop {
-        let g = m.lock().unwrap();
-
-        let c2 = c.clone();
-        let m2 = m.clone();
-
-        let notified = Arc::new(AtomicBool::new(false));
-        let notified_copy = notified.clone();
-
-        let t = thread::spawn(move || {
-            let _g = m2.lock().unwrap();
-            thread::sleep(Duration::from_millis(1));
-            notified_copy.store(true, Ordering::Relaxed);
-            c2.notify_one();
-        });
-        let (g, timeout_res) = c.wait_timeout(g, Duration::from_millis(u64::MAX)).unwrap();
-        assert!(!timeout_res.timed_out());
-        // spurious wakeups mean this isn't necessarily true
-        // so execute test again, if not notified
-        if !notified.load(Ordering::Relaxed) {
-            t.join().unwrap();
-            continue;
-        }
-        drop(g);
-
-        t.join().unwrap();
-
-        break;
-    }
-}
diff --git a/library/std/src/sync/poison/mutex.rs b/library/std/src/sync/poison/mutex.rs
index fb43ada6375..9362c764173 100644
--- a/library/std/src/sync/poison/mutex.rs
+++ b/library/std/src/sync/poison/mutex.rs
@@ -1,6 +1,3 @@
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
 use crate::cell::UnsafeCell;
 use crate::fmt;
 use crate::marker::PhantomData;
diff --git a/library/std/src/sync/poison/mutex/tests.rs b/library/std/src/sync/poison/mutex/tests.rs
deleted file mode 100644
index 395c8aada08..00000000000
--- a/library/std/src/sync/poison/mutex/tests.rs
+++ /dev/null
@@ -1,442 +0,0 @@
-use crate::fmt::Debug;
-use crate::ops::FnMut;
-use crate::panic::{self, AssertUnwindSafe};
-use crate::sync::atomic::{AtomicUsize, Ordering};
-use crate::sync::mpsc::channel;
-use crate::sync::{Arc, Condvar, MappedMutexGuard, Mutex, MutexGuard, TryLockError};
-use crate::{hint, mem, thread};
-
-struct Packet<T>(Arc<(Mutex<T>, Condvar)>);
-
-#[derive(Eq, PartialEq, Debug)]
-struct NonCopy(i32);
-
-#[derive(Eq, PartialEq, Debug)]
-struct NonCopyNeedsDrop(i32);
-
-impl Drop for NonCopyNeedsDrop {
-    fn drop(&mut self) {
-        hint::black_box(());
-    }
-}
-
-#[test]
-fn test_needs_drop() {
-    assert!(!mem::needs_drop::<NonCopy>());
-    assert!(mem::needs_drop::<NonCopyNeedsDrop>());
-}
-
-#[derive(Clone, Eq, PartialEq, Debug)]
-struct Cloneable(i32);
-
-#[test]
-fn smoke() {
-    let m = Mutex::new(());
-    drop(m.lock().unwrap());
-    drop(m.lock().unwrap());
-}
-
-#[test]
-fn lots_and_lots() {
-    const J: u32 = 1000;
-    const K: u32 = 3;
-
-    let m = Arc::new(Mutex::new(0));
-
-    fn inc(m: &Mutex<u32>) {
-        for _ in 0..J {
-            *m.lock().unwrap() += 1;
-        }
-    }
-
-    let (tx, rx) = channel();
-    for _ in 0..K {
-        let tx2 = tx.clone();
-        let m2 = m.clone();
-        thread::spawn(move || {
-            inc(&m2);
-            tx2.send(()).unwrap();
-        });
-        let tx2 = tx.clone();
-        let m2 = m.clone();
-        thread::spawn(move || {
-            inc(&m2);
-            tx2.send(()).unwrap();
-        });
-    }
-
-    drop(tx);
-    for _ in 0..2 * K {
-        rx.recv().unwrap();
-    }
-    assert_eq!(*m.lock().unwrap(), J * K * 2);
-}
-
-#[test]
-fn try_lock() {
-    let m = Mutex::new(());
-    *m.try_lock().unwrap() = ();
-}
-
-fn new_poisoned_mutex<T>(value: T) -> Mutex<T> {
-    let mutex = Mutex::new(value);
-
-    let catch_unwind_result = panic::catch_unwind(AssertUnwindSafe(|| {
-        let _guard = mutex.lock().unwrap();
-
-        panic!("test panic to poison mutex");
-    }));
-
-    assert!(catch_unwind_result.is_err());
-    assert!(mutex.is_poisoned());
-
-    mutex
-}
-
-#[test]
-fn test_into_inner() {
-    let m = Mutex::new(NonCopy(10));
-    assert_eq!(m.into_inner().unwrap(), NonCopy(10));
-}
-
-#[test]
-fn test_into_inner_drop() {
-    struct Foo(Arc<AtomicUsize>);
-    impl Drop for Foo {
-        fn drop(&mut self) {
-            self.0.fetch_add(1, Ordering::SeqCst);
-        }
-    }
-    let num_drops = Arc::new(AtomicUsize::new(0));
-    let m = Mutex::new(Foo(num_drops.clone()));
-    assert_eq!(num_drops.load(Ordering::SeqCst), 0);
-    {
-        let _inner = m.into_inner().unwrap();
-        assert_eq!(num_drops.load(Ordering::SeqCst), 0);
-    }
-    assert_eq!(num_drops.load(Ordering::SeqCst), 1);
-}
-
-#[test]
-fn test_into_inner_poison() {
-    let m = new_poisoned_mutex(NonCopy(10));
-
-    match m.into_inner() {
-        Err(e) => assert_eq!(e.into_inner(), NonCopy(10)),
-        Ok(x) => panic!("into_inner of poisoned Mutex is Ok: {x:?}"),
-    }
-}
-
-#[test]
-fn test_get_cloned() {
-    let m = Mutex::new(Cloneable(10));
-
-    assert_eq!(m.get_cloned().unwrap(), Cloneable(10));
-}
-
-#[test]
-fn test_get_cloned_poison() {
-    let m = new_poisoned_mutex(Cloneable(10));
-
-    match m.get_cloned() {
-        Err(e) => assert_eq!(e.into_inner(), ()),
-        Ok(x) => panic!("get of poisoned Mutex is Ok: {x:?}"),
-    }
-}
-
-#[test]
-fn test_get_mut() {
-    let mut m = Mutex::new(NonCopy(10));
-    *m.get_mut().unwrap() = NonCopy(20);
-    assert_eq!(m.into_inner().unwrap(), NonCopy(20));
-}
-
-#[test]
-fn test_get_mut_poison() {
-    let mut m = new_poisoned_mutex(NonCopy(10));
-
-    match m.get_mut() {
-        Err(e) => assert_eq!(*e.into_inner(), NonCopy(10)),
-        Ok(x) => panic!("get_mut of poisoned Mutex is Ok: {x:?}"),
-    }
-}
-
-#[test]
-fn test_set() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = Mutex::new(init());
-
-        assert_eq!(*m.lock().unwrap(), init());
-        m.set(value()).unwrap();
-        assert_eq!(*m.lock().unwrap(), value());
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
-fn test_set_poison() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = new_poisoned_mutex(init());
-
-        match m.set(value()) {
-            Err(e) => {
-                assert_eq!(e.into_inner(), value());
-                assert_eq!(m.into_inner().unwrap_err().into_inner(), init());
-            }
-            Ok(x) => panic!("set of poisoned Mutex is Ok: {x:?}"),
-        }
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
-fn test_replace() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = Mutex::new(init());
-
-        assert_eq!(*m.lock().unwrap(), init());
-        assert_eq!(m.replace(value()).unwrap(), init());
-        assert_eq!(*m.lock().unwrap(), value());
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
-fn test_replace_poison() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = new_poisoned_mutex(init());
-
-        match m.replace(value()) {
-            Err(e) => {
-                assert_eq!(e.into_inner(), value());
-                assert_eq!(m.into_inner().unwrap_err().into_inner(), init());
-            }
-            Ok(x) => panic!("replace of poisoned Mutex is Ok: {x:?}"),
-        }
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
-fn test_mutex_arc_condvar() {
-    let packet = Packet(Arc::new((Mutex::new(false), Condvar::new())));
-    let packet2 = Packet(packet.0.clone());
-    let (tx, rx) = channel();
-    let _t = thread::spawn(move || {
-        // wait until parent gets in
-        rx.recv().unwrap();
-        let &(ref lock, ref cvar) = &*packet2.0;
-        let mut lock = lock.lock().unwrap();
-        *lock = true;
-        cvar.notify_one();
-    });
-
-    let &(ref lock, ref cvar) = &*packet.0;
-    let mut lock = lock.lock().unwrap();
-    tx.send(()).unwrap();
-    assert!(!*lock);
-    while !*lock {
-        lock = cvar.wait(lock).unwrap();
-    }
-}
-
-#[test]
-fn test_arc_condvar_poison() {
-    let packet = Packet(Arc::new((Mutex::new(1), Condvar::new())));
-    let packet2 = Packet(packet.0.clone());
-    let (tx, rx) = channel();
-
-    let _t = thread::spawn(move || -> () {
-        rx.recv().unwrap();
-        let &(ref lock, ref cvar) = &*packet2.0;
-        let _g = lock.lock().unwrap();
-        cvar.notify_one();
-        // Parent should fail when it wakes up.
-        panic!();
-    });
-
-    let &(ref lock, ref cvar) = &*packet.0;
-    let mut lock = lock.lock().unwrap();
-    tx.send(()).unwrap();
-    while *lock == 1 {
-        match cvar.wait(lock) {
-            Ok(l) => {
-                lock = l;
-                assert_eq!(*lock, 1);
-            }
-            Err(..) => break,
-        }
-    }
-}
-
-#[test]
-fn test_mutex_arc_poison() {
-    let arc = Arc::new(Mutex::new(1));
-    assert!(!arc.is_poisoned());
-    let arc2 = arc.clone();
-    let _ = thread::spawn(move || {
-        let lock = arc2.lock().unwrap();
-        assert_eq!(*lock, 2); // deliberate assertion failure to poison the mutex
-    })
-    .join();
-    assert!(arc.lock().is_err());
-    assert!(arc.is_poisoned());
-}
-
-#[test]
-fn test_mutex_arc_poison_mapped() {
-    let arc = Arc::new(Mutex::new(1));
-    assert!(!arc.is_poisoned());
-    let arc2 = arc.clone();
-    let _ = thread::spawn(move || {
-        let lock = arc2.lock().unwrap();
-        let lock = MutexGuard::map(lock, |val| val);
-        assert_eq!(*lock, 2); // deliberate assertion failure to poison the mutex
-    })
-    .join();
-    assert!(arc.lock().is_err());
-    assert!(arc.is_poisoned());
-}
-
-#[test]
-fn test_mutex_arc_nested() {
-    // Tests nested mutexes and access
-    // to underlying data.
-    let arc = Arc::new(Mutex::new(1));
-    let arc2 = Arc::new(Mutex::new(arc));
-    let (tx, rx) = channel();
-    let _t = thread::spawn(move || {
-        let lock = arc2.lock().unwrap();
-        let lock2 = lock.lock().unwrap();
-        assert_eq!(*lock2, 1);
-        tx.send(()).unwrap();
-    });
-    rx.recv().unwrap();
-}
-
-#[test]
-fn test_mutex_arc_access_in_unwind() {
-    let arc = Arc::new(Mutex::new(1));
-    let arc2 = arc.clone();
-    let _ = thread::spawn(move || -> () {
-        struct Unwinder {
-            i: Arc<Mutex<i32>>,
-        }
-        impl Drop for Unwinder {
-            fn drop(&mut self) {
-                *self.i.lock().unwrap() += 1;
-            }
-        }
-        let _u = Unwinder { i: arc2 };
-        panic!();
-    })
-    .join();
-    let lock = arc.lock().unwrap();
-    assert_eq!(*lock, 2);
-}
-
-#[test]
-fn test_mutex_unsized() {
-    let mutex: &Mutex<[i32]> = &Mutex::new([1, 2, 3]);
-    {
-        let b = &mut *mutex.lock().unwrap();
-        b[0] = 4;
-        b[2] = 5;
-    }
-    let comp: &[i32] = &[4, 2, 5];
-    assert_eq!(&*mutex.lock().unwrap(), comp);
-}
-
-#[test]
-fn test_mapping_mapped_guard() {
-    let arr = [0; 4];
-    let mut lock = Mutex::new(arr);
-    let guard = lock.lock().unwrap();
-    let guard = MutexGuard::map(guard, |arr| &mut arr[..2]);
-    let mut guard = MappedMutexGuard::map(guard, |slice| &mut slice[1..]);
-    assert_eq!(guard.len(), 1);
-    guard[0] = 42;
-    drop(guard);
-    assert_eq!(*lock.get_mut().unwrap(), [0, 42, 0, 0]);
-}
-
-#[test]
-fn panic_while_mapping_unlocked_poison() {
-    let lock = Mutex::new(());
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.lock().unwrap();
-        let _guard = MutexGuard::map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_lock() {
-        Ok(_) => panic!("panicking in a MutexGuard::map closure should poison the Mutex"),
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a MutexGuard::map closure should unlock the mutex")
-        }
-        Err(TryLockError::Poisoned(_)) => {}
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.lock().unwrap();
-        let _guard = MutexGuard::try_map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_lock() {
-        Ok(_) => panic!("panicking in a MutexGuard::try_map closure should poison the Mutex"),
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a MutexGuard::try_map closure should unlock the mutex")
-        }
-        Err(TryLockError::Poisoned(_)) => {}
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.lock().unwrap();
-        let guard = MutexGuard::map::<(), _>(guard, |val| val);
-        let _guard = MappedMutexGuard::map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_lock() {
-        Ok(_) => panic!("panicking in a MappedMutexGuard::map closure should poison the Mutex"),
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a MappedMutexGuard::map closure should unlock the mutex")
-        }
-        Err(TryLockError::Poisoned(_)) => {}
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.lock().unwrap();
-        let guard = MutexGuard::map::<(), _>(guard, |val| val);
-        let _guard = MappedMutexGuard::try_map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_lock() {
-        Ok(_) => panic!("panicking in a MappedMutexGuard::try_map closure should poison the Mutex"),
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a MappedMutexGuard::try_map closure should unlock the mutex")
-        }
-        Err(TryLockError::Poisoned(_)) => {}
-    }
-
-    drop(lock);
-}
diff --git a/library/std/src/sync/poison/once.rs b/library/std/src/sync/poison/once.rs
index 528b11ca0c1..d2938b7a0c1 100644
--- a/library/std/src/sync/poison/once.rs
+++ b/library/std/src/sync/poison/once.rs
@@ -3,9 +3,6 @@
 //! This primitive is meant to be used to run one-time initialization. An
 //! example use case would be for initializing an FFI library.
 
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
 use crate::fmt;
 use crate::panic::{RefUnwindSafe, UnwindSafe};
 use crate::sys::sync as sys;
diff --git a/library/std/src/sync/poison/once/tests.rs b/library/std/src/sync/poison/once/tests.rs
deleted file mode 100644
index ce96468aeb6..00000000000
--- a/library/std/src/sync/poison/once/tests.rs
+++ /dev/null
@@ -1,162 +0,0 @@
-use super::Once;
-use crate::sync::atomic::AtomicBool;
-use crate::sync::atomic::Ordering::Relaxed;
-use crate::sync::mpsc::channel;
-use crate::time::Duration;
-use crate::{panic, thread};
-
-#[test]
-fn smoke_once() {
-    static O: Once = Once::new();
-    let mut a = 0;
-    O.call_once(|| a += 1);
-    assert_eq!(a, 1);
-    O.call_once(|| a += 1);
-    assert_eq!(a, 1);
-}
-
-#[test]
-fn stampede_once() {
-    static O: Once = Once::new();
-    static mut RUN: bool = false;
-
-    let (tx, rx) = channel();
-    for _ in 0..10 {
-        let tx = tx.clone();
-        thread::spawn(move || {
-            for _ in 0..4 {
-                thread::yield_now()
-            }
-            unsafe {
-                O.call_once(|| {
-                    assert!(!RUN);
-                    RUN = true;
-                });
-                assert!(RUN);
-            }
-            tx.send(()).unwrap();
-        });
-    }
-
-    unsafe {
-        O.call_once(|| {
-            assert!(!RUN);
-            RUN = true;
-        });
-        assert!(RUN);
-    }
-
-    for _ in 0..10 {
-        rx.recv().unwrap();
-    }
-}
-
-#[test]
-fn poison_bad() {
-    static O: Once = Once::new();
-
-    // poison the once
-    let t = panic::catch_unwind(|| {
-        O.call_once(|| panic!());
-    });
-    assert!(t.is_err());
-
-    // poisoning propagates
-    let t = panic::catch_unwind(|| {
-        O.call_once(|| {});
-    });
-    assert!(t.is_err());
-
-    // we can subvert poisoning, however
-    let mut called = false;
-    O.call_once_force(|p| {
-        called = true;
-        assert!(p.is_poisoned())
-    });
-    assert!(called);
-
-    // once any success happens, we stop propagating the poison
-    O.call_once(|| {});
-}
-
-#[test]
-fn wait_for_force_to_finish() {
-    static O: Once = Once::new();
-
-    // poison the once
-    let t = panic::catch_unwind(|| {
-        O.call_once(|| panic!());
-    });
-    assert!(t.is_err());
-
-    // make sure someone's waiting inside the once via a force
-    let (tx1, rx1) = channel();
-    let (tx2, rx2) = channel();
-    let t1 = thread::spawn(move || {
-        O.call_once_force(|p| {
-            assert!(p.is_poisoned());
-            tx1.send(()).unwrap();
-            rx2.recv().unwrap();
-        });
-    });
-
-    rx1.recv().unwrap();
-
-    // put another waiter on the once
-    let t2 = thread::spawn(|| {
-        let mut called = false;
-        O.call_once(|| {
-            called = true;
-        });
-        assert!(!called);
-    });
-
-    tx2.send(()).unwrap();
-
-    assert!(t1.join().is_ok());
-    assert!(t2.join().is_ok());
-}
-
-#[test]
-fn wait() {
-    for _ in 0..50 {
-        let val = AtomicBool::new(false);
-        let once = Once::new();
-
-        thread::scope(|s| {
-            for _ in 0..4 {
-                s.spawn(|| {
-                    once.wait();
-                    assert!(val.load(Relaxed));
-                });
-            }
-
-            once.call_once(|| val.store(true, Relaxed));
-        });
-    }
-}
-
-#[test]
-fn wait_on_poisoned() {
-    let once = Once::new();
-
-    panic::catch_unwind(|| once.call_once(|| panic!())).unwrap_err();
-    panic::catch_unwind(|| once.wait()).unwrap_err();
-}
-
-#[test]
-fn wait_force_on_poisoned() {
-    let once = Once::new();
-
-    thread::scope(|s| {
-        panic::catch_unwind(|| once.call_once(|| panic!())).unwrap_err();
-
-        s.spawn(|| {
-            thread::sleep(Duration::from_millis(100));
-
-            once.call_once_force(|_| {});
-        });
-
-        once.wait_force();
-    })
-}
diff --git a/library/std/src/sync/poison/rwlock.rs b/library/std/src/sync/poison/rwlock.rs
index 1519baf99a8..f9d9321f5f2 100644
--- a/library/std/src/sync/poison/rwlock.rs
+++ b/library/std/src/sync/poison/rwlock.rs
@@ -1,6 +1,3 @@
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
 use crate::cell::UnsafeCell;
 use crate::fmt;
 use crate::marker::PhantomData;
diff --git a/library/std/src/sync/poison/rwlock/tests.rs b/library/std/src/sync/poison/rwlock/tests.rs
deleted file mode 100644
index 057c2f1a5d7..00000000000
--- a/library/std/src/sync/poison/rwlock/tests.rs
+++ /dev/null
@@ -1,729 +0,0 @@
-use rand::Rng;
-
-use crate::fmt::Debug;
-use crate::ops::FnMut;
-use crate::panic::{self, AssertUnwindSafe};
-use crate::sync::atomic::{AtomicUsize, Ordering};
-use crate::sync::mpsc::channel;
-use crate::sync::{
-    Arc, MappedRwLockReadGuard, MappedRwLockWriteGuard, RwLock, RwLockReadGuard, RwLockWriteGuard,
-    TryLockError,
-};
-use crate::{hint, mem, thread};
-
-#[derive(Eq, PartialEq, Debug)]
-struct NonCopy(i32);
-
-#[derive(Eq, PartialEq, Debug)]
-struct NonCopyNeedsDrop(i32);
-
-impl Drop for NonCopyNeedsDrop {
-    fn drop(&mut self) {
-        hint::black_box(());
-    }
-}
-
-#[test]
-fn test_needs_drop() {
-    assert!(!mem::needs_drop::<NonCopy>());
-    assert!(mem::needs_drop::<NonCopyNeedsDrop>());
-}
-
-#[derive(Clone, Eq, PartialEq, Debug)]
-struct Cloneable(i32);
-
-#[test]
-fn smoke() {
-    let l = RwLock::new(());
-    drop(l.read().unwrap());
-    drop(l.write().unwrap());
-    drop((l.read().unwrap(), l.read().unwrap()));
-    drop(l.write().unwrap());
-}
-
-#[test]
-// FIXME: On macOS we use a provenance-incorrect implementation and Miri
-// catches that issue with a chance of around 1/1000.
-// See <https://github.com/rust-lang/rust/issues/121950> for details.
-#[cfg_attr(all(miri, target_os = "macos"), ignore)]
-fn frob() {
-    const N: u32 = 10;
-    const M: usize = if cfg!(miri) { 100 } else { 1000 };
-
-    let r = Arc::new(RwLock::new(()));
-
-    let (tx, rx) = channel::<()>();
-    for _ in 0..N {
-        let tx = tx.clone();
-        let r = r.clone();
-        thread::spawn(move || {
-            let mut rng = crate::test_helpers::test_rng();
-            for _ in 0..M {
-                if rng.gen_bool(1.0 / (N as f64)) {
-                    drop(r.write().unwrap());
-                } else {
-                    drop(r.read().unwrap());
-                }
-            }
-            drop(tx);
-        });
-    }
-    drop(tx);
-    let _ = rx.recv();
-}
-
-#[test]
-fn test_rw_arc_poison_wr() {
-    let arc = Arc::new(RwLock::new(1));
-    let arc2 = arc.clone();
-    let _: Result<(), _> = thread::spawn(move || {
-        let _lock = arc2.write().unwrap();
-        panic!();
-    })
-    .join();
-    assert!(arc.read().is_err());
-}
-
-#[test]
-fn test_rw_arc_poison_mapped_w_r() {
-    let arc = Arc::new(RwLock::new(1));
-    let arc2 = arc.clone();
-    let _: Result<(), _> = thread::spawn(move || {
-        let lock = arc2.write().unwrap();
-        let _lock = RwLockWriteGuard::map(lock, |val| val);
-        panic!();
-    })
-    .join();
-    assert!(arc.read().is_err());
-}
-
-#[test]
-fn test_rw_arc_poison_ww() {
-    let arc = Arc::new(RwLock::new(1));
-    assert!(!arc.is_poisoned());
-    let arc2 = arc.clone();
-    let _: Result<(), _> = thread::spawn(move || {
-        let _lock = arc2.write().unwrap();
-        panic!();
-    })
-    .join();
-    assert!(arc.write().is_err());
-    assert!(arc.is_poisoned());
-}
-
-#[test]
-fn test_rw_arc_poison_mapped_w_w() {
-    let arc = Arc::new(RwLock::new(1));
-    let arc2 = arc.clone();
-    let _: Result<(), _> = thread::spawn(move || {
-        let lock = arc2.write().unwrap();
-        let _lock = RwLockWriteGuard::map(lock, |val| val);
-        panic!();
-    })
-    .join();
-    assert!(arc.write().is_err());
-    assert!(arc.is_poisoned());
-}
-
-#[test]
-fn test_rw_arc_no_poison_rr() {
-    let arc = Arc::new(RwLock::new(1));
-    let arc2 = arc.clone();
-    let _: Result<(), _> = thread::spawn(move || {
-        let _lock = arc2.read().unwrap();
-        panic!();
-    })
-    .join();
-    let lock = arc.read().unwrap();
-    assert_eq!(*lock, 1);
-}
-
-#[test]
-fn test_rw_arc_no_poison_mapped_r_r() {
-    let arc = Arc::new(RwLock::new(1));
-    let arc2 = arc.clone();
-    let _: Result<(), _> = thread::spawn(move || {
-        let lock = arc2.read().unwrap();
-        let _lock = RwLockReadGuard::map(lock, |val| val);
-        panic!();
-    })
-    .join();
-    let lock = arc.read().unwrap();
-    assert_eq!(*lock, 1);
-}
-
-#[test]
-fn test_rw_arc_no_poison_rw() {
-    let arc = Arc::new(RwLock::new(1));
-    let arc2 = arc.clone();
-    let _: Result<(), _> = thread::spawn(move || {
-        let _lock = arc2.read().unwrap();
-        panic!()
-    })
-    .join();
-    let lock = arc.write().unwrap();
-    assert_eq!(*lock, 1);
-}
-
-#[test]
-fn test_rw_arc_no_poison_mapped_r_w() {
-    let arc = Arc::new(RwLock::new(1));
-    let arc2 = arc.clone();
-    let _: Result<(), _> = thread::spawn(move || {
-        let lock = arc2.read().unwrap();
-        let _lock = RwLockReadGuard::map(lock, |val| val);
-        panic!();
-    })
-    .join();
-    let lock = arc.write().unwrap();
-    assert_eq!(*lock, 1);
-}
-
-#[test]
-fn test_rw_arc() {
-    let arc = Arc::new(RwLock::new(0));
-    let arc2 = arc.clone();
-    let (tx, rx) = channel();
-
-    thread::spawn(move || {
-        let mut lock = arc2.write().unwrap();
-        for _ in 0..10 {
-            let tmp = *lock;
-            *lock = -1;
-            thread::yield_now();
-            *lock = tmp + 1;
-        }
-        tx.send(()).unwrap();
-    });
-
-    // Readers try to catch the writer in the act
-    let mut children = Vec::new();
-    for _ in 0..5 {
-        let arc3 = arc.clone();
-        children.push(thread::spawn(move || {
-            let lock = arc3.read().unwrap();
-            assert!(*lock >= 0);
-        }));
-    }
-
-    // Wait for children to pass their asserts
-    for r in children {
-        assert!(r.join().is_ok());
-    }
-
-    // Wait for writer to finish
-    rx.recv().unwrap();
-    let lock = arc.read().unwrap();
-    assert_eq!(*lock, 10);
-}
-
-#[test]
-fn test_rw_arc_access_in_unwind() {
-    let arc = Arc::new(RwLock::new(1));
-    let arc2 = arc.clone();
-    let _ = thread::spawn(move || -> () {
-        struct Unwinder {
-            i: Arc<RwLock<isize>>,
-        }
-        impl Drop for Unwinder {
-            fn drop(&mut self) {
-                let mut lock = self.i.write().unwrap();
-                *lock += 1;
-            }
-        }
-        let _u = Unwinder { i: arc2 };
-        panic!();
-    })
-    .join();
-    let lock = arc.read().unwrap();
-    assert_eq!(*lock, 2);
-}
-
-#[test]
-fn test_rwlock_unsized() {
-    let rw: &RwLock<[i32]> = &RwLock::new([1, 2, 3]);
-    {
-        let b = &mut *rw.write().unwrap();
-        b[0] = 4;
-        b[2] = 5;
-    }
-    let comp: &[i32] = &[4, 2, 5];
-    assert_eq!(&*rw.read().unwrap(), comp);
-}
-
-#[test]
-fn test_rwlock_try_write() {
-    let lock = RwLock::new(0isize);
-    let read_guard = lock.read().unwrap();
-
-    let write_result = lock.try_write();
-    match write_result {
-        Err(TryLockError::WouldBlock) => (),
-        Ok(_) => assert!(false, "try_write should not succeed while read_guard is in scope"),
-        Err(_) => assert!(false, "unexpected error"),
-    }
-
-    drop(read_guard);
-    let mapped_read_guard = RwLockReadGuard::map(lock.read().unwrap(), |_| &());
-
-    let write_result = lock.try_write();
-    match write_result {
-        Err(TryLockError::WouldBlock) => (),
-        Ok(_) => assert!(false, "try_write should not succeed while mapped_read_guard is in scope"),
-        Err(_) => assert!(false, "unexpected error"),
-    }
-
-    drop(mapped_read_guard);
-}
-
-fn new_poisoned_rwlock<T>(value: T) -> RwLock<T> {
-    let lock = RwLock::new(value);
-
-    let catch_unwind_result = panic::catch_unwind(AssertUnwindSafe(|| {
-        let _guard = lock.write().unwrap();
-
-        panic!("test panic to poison RwLock");
-    }));
-
-    assert!(catch_unwind_result.is_err());
-    assert!(lock.is_poisoned());
-
-    lock
-}
-
-#[test]
-fn test_into_inner() {
-    let m = RwLock::new(NonCopy(10));
-    assert_eq!(m.into_inner().unwrap(), NonCopy(10));
-}
-
-#[test]
-fn test_into_inner_drop() {
-    struct Foo(Arc<AtomicUsize>);
-    impl Drop for Foo {
-        fn drop(&mut self) {
-            self.0.fetch_add(1, Ordering::SeqCst);
-        }
-    }
-    let num_drops = Arc::new(AtomicUsize::new(0));
-    let m = RwLock::new(Foo(num_drops.clone()));
-    assert_eq!(num_drops.load(Ordering::SeqCst), 0);
-    {
-        let _inner = m.into_inner().unwrap();
-        assert_eq!(num_drops.load(Ordering::SeqCst), 0);
-    }
-    assert_eq!(num_drops.load(Ordering::SeqCst), 1);
-}
-
-#[test]
-fn test_into_inner_poison() {
-    let m = new_poisoned_rwlock(NonCopy(10));
-
-    match m.into_inner() {
-        Err(e) => assert_eq!(e.into_inner(), NonCopy(10)),
-        Ok(x) => panic!("into_inner of poisoned RwLock is Ok: {x:?}"),
-    }
-}
-
-#[test]
-fn test_get_cloned() {
-    let m = RwLock::new(Cloneable(10));
-
-    assert_eq!(m.get_cloned().unwrap(), Cloneable(10));
-}
-
-#[test]
-fn test_get_cloned_poison() {
-    let m = new_poisoned_rwlock(Cloneable(10));
-
-    match m.get_cloned() {
-        Err(e) => assert_eq!(e.into_inner(), ()),
-        Ok(x) => panic!("get of poisoned RwLock is Ok: {x:?}"),
-    }
-}
-
-#[test]
-fn test_get_mut() {
-    let mut m = RwLock::new(NonCopy(10));
-    *m.get_mut().unwrap() = NonCopy(20);
-    assert_eq!(m.into_inner().unwrap(), NonCopy(20));
-}
-
-#[test]
-fn test_get_mut_poison() {
-    let mut m = new_poisoned_rwlock(NonCopy(10));
-
-    match m.get_mut() {
-        Err(e) => assert_eq!(*e.into_inner(), NonCopy(10)),
-        Ok(x) => panic!("get_mut of poisoned RwLock is Ok: {x:?}"),
-    }
-}
-
-#[test]
-fn test_set() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = RwLock::new(init());
-
-        assert_eq!(*m.read().unwrap(), init());
-        m.set(value()).unwrap();
-        assert_eq!(*m.read().unwrap(), value());
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
-fn test_set_poison() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = new_poisoned_rwlock(init());
-
-        match m.set(value()) {
-            Err(e) => {
-                assert_eq!(e.into_inner(), value());
-                assert_eq!(m.into_inner().unwrap_err().into_inner(), init());
-            }
-            Ok(x) => panic!("set of poisoned RwLock is Ok: {x:?}"),
-        }
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
-fn test_replace() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = RwLock::new(init());
-
-        assert_eq!(*m.read().unwrap(), init());
-        assert_eq!(m.replace(value()).unwrap(), init());
-        assert_eq!(*m.read().unwrap(), value());
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
-fn test_replace_poison() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = new_poisoned_rwlock(init());
-
-        match m.replace(value()) {
-            Err(e) => {
-                assert_eq!(e.into_inner(), value());
-                assert_eq!(m.into_inner().unwrap_err().into_inner(), init());
-            }
-            Ok(x) => panic!("replace of poisoned RwLock is Ok: {x:?}"),
-        }
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
-fn test_read_guard_covariance() {
-    fn do_stuff<'a>(_: RwLockReadGuard<'_, &'a i32>, _: &'a i32) {}
-    let j: i32 = 5;
-    let lock = RwLock::new(&j);
-    {
-        let i = 6;
-        do_stuff(lock.read().unwrap(), &i);
-    }
-    drop(lock);
-}
-
-#[test]
-fn test_mapped_read_guard_covariance() {
-    fn do_stuff<'a>(_: MappedRwLockReadGuard<'_, &'a i32>, _: &'a i32) {}
-    let j: i32 = 5;
-    let lock = RwLock::new((&j, &j));
-    {
-        let i = 6;
-        let guard = lock.read().unwrap();
-        let guard = RwLockReadGuard::map(guard, |(val, _val)| val);
-        do_stuff(guard, &i);
-    }
-    drop(lock);
-}
-
-#[test]
-fn test_mapping_mapped_guard() {
-    let arr = [0; 4];
-    let mut lock = RwLock::new(arr);
-    let guard = lock.write().unwrap();
-    let guard = RwLockWriteGuard::map(guard, |arr| &mut arr[..2]);
-    let mut guard = MappedRwLockWriteGuard::map(guard, |slice| &mut slice[1..]);
-    assert_eq!(guard.len(), 1);
-    guard[0] = 42;
-    drop(guard);
-    assert_eq!(*lock.get_mut().unwrap(), [0, 42, 0, 0]);
-
-    let guard = lock.read().unwrap();
-    let guard = RwLockReadGuard::map(guard, |arr| &arr[..2]);
-    let guard = MappedRwLockReadGuard::map(guard, |slice| &slice[1..]);
-    assert_eq!(*guard, [42]);
-    drop(guard);
-    assert_eq!(*lock.get_mut().unwrap(), [0, 42, 0, 0]);
-}
-
-#[test]
-fn panic_while_mapping_read_unlocked_no_poison() {
-    let lock = RwLock::new(());
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.read().unwrap();
-        let _guard = RwLockReadGuard::map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_write() {
-        Ok(_) => {}
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a RwLockReadGuard::map closure should release the read lock")
-        }
-        Err(TryLockError::Poisoned(_)) => {
-            panic!("panicking in a RwLockReadGuard::map closure should not poison the RwLock")
-        }
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.read().unwrap();
-        let _guard = RwLockReadGuard::try_map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_write() {
-        Ok(_) => {}
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a RwLockReadGuard::try_map closure should release the read lock")
-        }
-        Err(TryLockError::Poisoned(_)) => {
-            panic!("panicking in a RwLockReadGuard::try_map closure should not poison the RwLock")
-        }
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.read().unwrap();
-        let guard = RwLockReadGuard::map::<(), _>(guard, |val| val);
-        let _guard = MappedRwLockReadGuard::map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_write() {
-        Ok(_) => {}
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a MappedRwLockReadGuard::map closure should release the read lock")
-        }
-        Err(TryLockError::Poisoned(_)) => {
-            panic!("panicking in a MappedRwLockReadGuard::map closure should not poison the RwLock")
-        }
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.read().unwrap();
-        let guard = RwLockReadGuard::map::<(), _>(guard, |val| val);
-        let _guard = MappedRwLockReadGuard::try_map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_write() {
-        Ok(_) => {}
-        Err(TryLockError::WouldBlock) => panic!(
-            "panicking in a MappedRwLockReadGuard::try_map closure should release the read lock"
-        ),
-        Err(TryLockError::Poisoned(_)) => panic!(
-            "panicking in a MappedRwLockReadGuard::try_map closure should not poison the RwLock"
-        ),
-    }
-
-    drop(lock);
-}
-
-#[test]
-fn panic_while_mapping_write_unlocked_poison() {
-    let lock = RwLock::new(());
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.write().unwrap();
-        let _guard = RwLockWriteGuard::map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_write() {
-        Ok(_) => panic!("panicking in a RwLockWriteGuard::map closure should poison the RwLock"),
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a RwLockWriteGuard::map closure should release the write lock")
-        }
-        Err(TryLockError::Poisoned(_)) => {}
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.write().unwrap();
-        let _guard = RwLockWriteGuard::try_map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_write() {
-        Ok(_) => {
-            panic!("panicking in a RwLockWriteGuard::try_map closure should poison the RwLock")
-        }
-        Err(TryLockError::WouldBlock) => {
-            panic!("panicking in a RwLockWriteGuard::try_map closure should release the write lock")
-        }
-        Err(TryLockError::Poisoned(_)) => {}
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.write().unwrap();
-        let guard = RwLockWriteGuard::map::<(), _>(guard, |val| val);
-        let _guard = MappedRwLockWriteGuard::map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_write() {
-        Ok(_) => {
-            panic!("panicking in a MappedRwLockWriteGuard::map closure should poison the RwLock")
-        }
-        Err(TryLockError::WouldBlock) => panic!(
-            "panicking in a MappedRwLockWriteGuard::map closure should release the write lock"
-        ),
-        Err(TryLockError::Poisoned(_)) => {}
-    }
-
-    let _ = panic::catch_unwind(|| {
-        let guard = lock.write().unwrap();
-        let guard = RwLockWriteGuard::map::<(), _>(guard, |val| val);
-        let _guard = MappedRwLockWriteGuard::try_map::<(), _>(guard, |_| panic!());
-    });
-
-    match lock.try_write() {
-        Ok(_) => panic!(
-            "panicking in a MappedRwLockWriteGuard::try_map closure should poison the RwLock"
-        ),
-        Err(TryLockError::WouldBlock) => panic!(
-            "panicking in a MappedRwLockWriteGuard::try_map closure should release the write lock"
-        ),
-        Err(TryLockError::Poisoned(_)) => {}
-    }
-
-    drop(lock);
-}
-
-#[test]
-fn test_downgrade_basic() {
-    let r = RwLock::new(());
-
-    let write_guard = r.write().unwrap();
-    let _read_guard = RwLockWriteGuard::downgrade(write_guard);
-}
-
-#[test]
-// FIXME: On macOS we use a provenance-incorrect implementation and Miri catches that issue.
-// See <https://github.com/rust-lang/rust/issues/121950> for details.
-#[cfg_attr(all(miri, target_os = "macos"), ignore)]
-fn test_downgrade_observe() {
-    // Taken from the test `test_rwlock_downgrade` from:
-    // https://github.com/Amanieu/parking_lot/blob/master/src/rwlock.rs
-
-    const W: usize = 20;
-    const N: usize = if cfg!(miri) { 40 } else { 100 };
-
-    // This test spawns `W` writer threads, where each will increment a counter `N` times, ensuring
-    // that the value they wrote has not changed after downgrading.
-
-    let rw = Arc::new(RwLock::new(0));
-
-    // Spawn the writers that will do `W * N` operations and checks.
-    let handles: Vec<_> = (0..W)
-        .map(|_| {
-            let rw = rw.clone();
-            thread::spawn(move || {
-                for _ in 0..N {
-                    // Increment the counter.
-                    let mut write_guard = rw.write().unwrap();
-                    *write_guard += 1;
-                    let cur_val = *write_guard;
-
-                    // Downgrade the lock to read mode, where the value protected cannot be modified.
-                    let read_guard = RwLockWriteGuard::downgrade(write_guard);
-                    assert_eq!(cur_val, *read_guard);
-                }
-            })
-        })
-        .collect();
-
-    for handle in handles {
-        handle.join().unwrap();
-    }
-
-    assert_eq!(*rw.read().unwrap(), W * N);
-}
-
-#[test]
-// FIXME: On macOS we use a provenance-incorrect implementation and Miri catches that issue.
-// See <https://github.com/rust-lang/rust/issues/121950> for details.
-#[cfg_attr(all(miri, target_os = "macos"), ignore)]
-fn test_downgrade_atomic() {
-    const NEW_VALUE: i32 = -1;
-
-    // This test checks that `downgrade` is atomic, meaning as soon as a write lock has been
-    // downgraded, the lock must be in read mode and no other threads can take the write lock to
-    // modify the protected value.
-
-    // `W` is the number of evil writer threads.
-    const W: usize = 20;
-    let rwlock = Arc::new(RwLock::new(0));
-
-    // Spawns many evil writer threads that will try and write to the locked value before the
-    // initial writer (who has the exclusive lock) can read after it downgrades.
-    // If the `RwLock` behaves correctly, then the initial writer should read the value it wrote
-    // itself as no other thread should be able to mutate the protected value.
-
-    // Put the lock in write mode, causing all future threads trying to access this go to sleep.
-    let mut main_write_guard = rwlock.write().unwrap();
-
-    // Spawn all of the evil writer threads. They will each increment the protected value by 1.
-    let handles: Vec<_> = (0..W)
-        .map(|_| {
-            let rwlock = rwlock.clone();
-            thread::spawn(move || {
-                // Will go to sleep since the main thread initially has the write lock.
-                let mut evil_guard = rwlock.write().unwrap();
-                *evil_guard += 1;
-            })
-        })
-        .collect();
-
-    // Wait for a good amount of time so that evil threads go to sleep.
-    // Note: this is not strictly necessary...
-    let eternity = crate::time::Duration::from_millis(42);
-    thread::sleep(eternity);
-
-    // Once everyone is asleep, set the value to `NEW_VALUE`.
-    *main_write_guard = NEW_VALUE;
-
-    // Atomically downgrade the write guard into a read guard.
-    let main_read_guard = RwLockWriteGuard::downgrade(main_write_guard);
-
-    // If the above is not atomic, then it would be possible for an evil thread to get in front of
-    // this read and change the value to be non-negative.
-    assert_eq!(*main_read_guard, NEW_VALUE, "`downgrade` was not atomic");
-
-    // Drop the main read guard and allow the evil writer threads to start incrementing.
-    drop(main_read_guard);
-
-    for handle in handles {
-        handle.join().unwrap();
-    }
-
-    let final_check = rwlock.read().unwrap();
-    assert_eq!(*final_check, W as i32 + NEW_VALUE);
-}
diff --git a/library/std/src/sync/reentrant_lock.rs b/library/std/src/sync/reentrant_lock.rs
index 0140e0d2129..e009eb410ef 100644
--- a/library/std/src/sync/reentrant_lock.rs
+++ b/library/std/src/sync/reentrant_lock.rs
@@ -1,6 +1,3 @@
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
 use cfg_if::cfg_if;
 
 use crate::cell::UnsafeCell;
@@ -324,7 +321,10 @@ impl<T: ?Sized> ReentrantLock<T> {
     /// Otherwise, an RAII guard is returned.
     ///
     /// This function does not block.
-    pub(crate) fn try_lock(&self) -> Option<ReentrantLockGuard<'_, T>> {
+    // FIXME maybe make it a public part of the API?
+    #[unstable(issue = "none", feature = "std_internals")]
+    #[doc(hidden)]
+    pub fn try_lock(&self) -> Option<ReentrantLockGuard<'_, T>> {
         let this_thread = current_id();
         // Safety: We only touch lock_count when we own the inner mutex.
         // Additionally, we only call `self.owner.set()` while holding
diff --git a/library/std/src/sync/reentrant_lock/tests.rs b/library/std/src/sync/reentrant_lock/tests.rs
deleted file mode 100644
index aeef0289d28..00000000000
--- a/library/std/src/sync/reentrant_lock/tests.rs
+++ /dev/null
@@ -1,53 +0,0 @@
-use super::ReentrantLock;
-use crate::cell::RefCell;
-use crate::sync::Arc;
-use crate::thread;
-
-#[test]
-fn smoke() {
-    let l = ReentrantLock::new(());
-    {
-        let a = l.lock();
-        {
-            let b = l.lock();
-            {
-                let c = l.lock();
-                assert_eq!(*c, ());
-            }
-            assert_eq!(*b, ());
-        }
-        assert_eq!(*a, ());
-    }
-}
-
-#[test]
-fn is_mutex() {
-    let l = Arc::new(ReentrantLock::new(RefCell::new(0)));
-    let l2 = l.clone();
-    let lock = l.lock();
-    let child = thread::spawn(move || {
-        let lock = l2.lock();
-        assert_eq!(*lock.borrow(), 4950);
-    });
-    for i in 0..100 {
-        let lock = l.lock();
-        *lock.borrow_mut() += i;
-    }
-    drop(lock);
-    child.join().unwrap();
-}
-
-#[test]
-fn trylock_works() {
-    let l = Arc::new(ReentrantLock::new(()));
-    let l2 = l.clone();
-    let _lock = l.try_lock();
-    let _lock2 = l.try_lock();
-    thread::spawn(move || {
-        let lock = l2.try_lock();
-        assert!(lock.is_none());
-    })
-    .join()
-    .unwrap();
-    let _lock3 = l.try_lock();
-}