diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs
index 04b7315e650a2..ae34fc653260e 100644
--- a/library/alloc/src/alloc.rs
+++ b/library/alloc/src/alloc.rs
@@ -10,9 +10,6 @@ use core::hint;
 #[cfg(not(test))]
 use core::ptr::{self, NonNull};
 
-#[cfg(test)]
-mod tests;
-
 extern "Rust" {
     // These are the magic symbols to call the global allocator. rustc generates
     // them to call `__rg_alloc` etc. if there is a `#[global_allocator]` attribute
diff --git a/library/alloc/src/collections/binary_heap/mod.rs b/library/alloc/src/collections/binary_heap/mod.rs
index 5d3997e14e3e9..116e0e73e9659 100644
--- a/library/alloc/src/collections/binary_heap/mod.rs
+++ b/library/alloc/src/collections/binary_heap/mod.rs
@@ -155,9 +155,6 @@ use crate::collections::TryReserveError;
 use crate::slice;
 use crate::vec::{self, AsVecIntoIter, Vec};
 
-#[cfg(test)]
-mod tests;
-
 /// A priority queue implemented with a binary heap.
 ///
 /// This will be a max-heap.
diff --git a/library/alloc/src/ffi/c_str.rs b/library/alloc/src/ffi/c_str.rs
index 9c074383a5ecb..c7d6d8a55c2e3 100644
--- a/library/alloc/src/ffi/c_str.rs
+++ b/library/alloc/src/ffi/c_str.rs
@@ -1,8 +1,5 @@
 //! [`CString`] and its related types.
 
-#[cfg(test)]
-mod tests;
-
 use core::borrow::Borrow;
 use core::ffi::{CStr, c_char};
 use core::num::NonZero;
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 927c3aa23b9f7..78cdeeb2866ef 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -239,8 +239,6 @@ pub mod string;
 pub mod sync;
 #[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync)))]
 pub mod task;
-#[cfg(test)]
-mod tests;
 pub mod vec;
 
 #[doc(hidden)]
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index b8bdd298c27ab..6cf41a3fa4e16 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -39,9 +39,6 @@ use crate::string::String;
 #[cfg(not(no_global_oom_handling))]
 use crate::vec::Vec;
 
-#[cfg(test)]
-mod tests;
-
 /// A soft limit on the amount of references that may be made to an `Arc`.
 ///
 /// Going above this limit will abort your program (although not
diff --git a/library/alloc/src/alloc/tests.rs b/library/alloc/tests/alloc.rs
similarity index 93%
rename from library/alloc/src/alloc/tests.rs
rename to library/alloc/tests/alloc.rs
index 5d6077f057a2c..1e722d667955c 100644
--- a/library/alloc/src/alloc/tests.rs
+++ b/library/alloc/tests/alloc.rs
@@ -1,10 +1,9 @@
-use super::*;
+use alloc::alloc::*;
+use alloc::boxed::Box;
 
 extern crate test;
 use test::Bencher;
 
-use crate::boxed::Box;
-
 #[test]
 fn allocate_zeroed() {
     unsafe {
diff --git a/library/alloc/src/ffi/c_str/tests.rs b/library/alloc/tests/c_str2.rs
similarity index 98%
rename from library/alloc/src/ffi/c_str/tests.rs
rename to library/alloc/tests/c_str2.rs
index d6b797347c2ec..0f4c27fa12322 100644
--- a/library/alloc/src/ffi/c_str/tests.rs
+++ b/library/alloc/tests/c_str2.rs
@@ -1,11 +1,12 @@
+use alloc::ffi::CString;
+use alloc::rc::Rc;
+use alloc::sync::Arc;
 use core::assert_matches::assert_matches;
-use core::ffi::FromBytesUntilNulError;
+use core::ffi::{CStr, FromBytesUntilNulError, c_char};
 #[allow(deprecated)]
 use core::hash::SipHasher13 as DefaultHasher;
 use core::hash::{Hash, Hasher};
 
-use super::*;
-
 #[test]
 fn c_to_rust() {
     let data = b"123\0";
diff --git a/library/alloc/src/collections/binary_heap/tests.rs b/library/alloc/tests/collections/binary_heap.rs
similarity index 99%
rename from library/alloc/src/collections/binary_heap/tests.rs
rename to library/alloc/tests/collections/binary_heap.rs
index ad0a020a1a961..55405ffe8c4f6 100644
--- a/library/alloc/src/collections/binary_heap/tests.rs
+++ b/library/alloc/tests/collections/binary_heap.rs
@@ -1,7 +1,9 @@
+use alloc::boxed::Box;
+use alloc::collections::binary_heap::*;
+use std::iter::TrustedLen;
+use std::mem;
 use std::panic::{AssertUnwindSafe, catch_unwind};
 
-use super::*;
-use crate::boxed::Box;
 use crate::testing::crash_test::{CrashTestDummy, Panic};
 
 #[test]
@@ -531,7 +533,7 @@ fn panic_safe() {
             self.0.partial_cmp(&other.0)
         }
     }
-    let mut rng = crate::test_helpers::test_rng();
+    let mut rng = crate::test_rng();
     const DATASZ: usize = 32;
     // Miri is too slow
     let ntest = if cfg!(miri) { 1 } else { 10 };
diff --git a/library/alloc/tests/collections/mod.rs b/library/alloc/tests/collections/mod.rs
new file mode 100644
index 0000000000000..e73f3aaef8c83
--- /dev/null
+++ b/library/alloc/tests/collections/mod.rs
@@ -0,0 +1 @@
+mod binary_heap;
diff --git a/library/alloc/tests/lib.rs b/library/alloc/tests/lib.rs
index bcab17e7b2ddc..393bdfe48b741 100644
--- a/library/alloc/tests/lib.rs
+++ b/library/alloc/tests/lib.rs
@@ -5,8 +5,10 @@
 #![feature(btree_extract_if)]
 #![feature(cow_is_borrowed)]
 #![feature(core_intrinsics)]
+#![feature(downcast_unchecked)]
 #![feature(extract_if)]
 #![feature(exact_size_is_empty)]
+#![feature(hashmap_internals)]
 #![feature(linked_list_cursors)]
 #![feature(map_try_insert)]
 #![feature(pattern)]
@@ -29,9 +31,11 @@
 #![feature(const_str_from_utf8)]
 #![feature(panic_update_hook)]
 #![feature(pointer_is_aligned_to)]
+#![feature(test)]
 #![feature(thin_box)]
 #![feature(drain_keep_rest)]
 #![feature(local_waker)]
+#![feature(str_as_str)]
 #![feature(strict_provenance_lints)]
 #![feature(vec_pop_if)]
 #![feature(unique_rc_arc)]
@@ -40,25 +44,33 @@
 #![deny(fuzzy_provenance_casts)]
 #![deny(unsafe_op_in_unsafe_fn)]
 
+extern crate test;
+
 use std::hash::{DefaultHasher, Hash, Hasher};
 
+mod alloc;
 mod arc;
 mod autotraits;
 mod borrow;
 mod boxed;
 mod btree_set_hash;
 mod c_str;
+mod c_str2;
+mod collections;
 mod const_fns;
 mod cow_str;
 mod fmt;
 mod heap;
 mod linked_list;
+mod misc_tests;
 mod rc;
 mod slice;
 mod sort;
 mod str;
 mod string;
+mod sync;
 mod task;
+mod testing;
 mod thin_box;
 mod vec;
 mod vec_deque;
@@ -69,6 +81,18 @@ fn hash<T: Hash>(t: &T) -> u64 {
     s.finish()
 }
 
+/// Copied from `std::test_helpers::test_rng`, since these tests rely on the
+/// seed not being the same for every RNG invocation too.
+fn test_rng() -> rand_xorshift::XorShiftRng {
+    use std::hash::{BuildHasher, Hash, Hasher};
+    let mut hasher = std::hash::RandomState::new().build_hasher();
+    std::panic::Location::caller().hash(&mut hasher);
+    let hc64 = hasher.finish();
+    let seed_vec = hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<Vec<u8>>();
+    let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
+    rand::SeedableRng::from_seed(seed)
+}
+
 // FIXME: Instantiated functions with i128 in the signature is not supported in Emscripten.
 // See https://github.com/kripken/emscripten-fastcomp/issues/169
 #[cfg(not(target_os = "emscripten"))]
diff --git a/library/alloc/src/tests.rs b/library/alloc/tests/misc_tests.rs
similarity index 100%
rename from library/alloc/src/tests.rs
rename to library/alloc/tests/misc_tests.rs
diff --git a/library/alloc/src/sync/tests.rs b/library/alloc/tests/sync.rs
similarity index 98%
rename from library/alloc/src/sync/tests.rs
rename to library/alloc/tests/sync.rs
index de5816fda974a..7a9a4abfdc672 100644
--- a/library/alloc/src/sync/tests.rs
+++ b/library/alloc/tests/sync.rs
@@ -1,14 +1,16 @@
+use alloc::sync::*;
+use std::alloc::{AllocError, Allocator, Layout};
+use std::any::Any;
 use std::clone::Clone;
 use std::mem::MaybeUninit;
 use std::option::Option::None;
+use std::ptr::NonNull;
 use std::sync::Mutex;
-use std::sync::atomic::AtomicUsize;
-use std::sync::atomic::Ordering::SeqCst;
+use std::sync::atomic::Ordering::*;
+use std::sync::atomic::{self, AtomicUsize};
 use std::sync::mpsc::channel;
 use std::thread;
 
-use super::*;
-
 struct Canary(*mut AtomicUsize);
 
 impl Drop for Canary {
diff --git a/library/alloc/tests/testing/crash_test.rs b/library/alloc/tests/testing/crash_test.rs
new file mode 100644
index 0000000000000..502fe6c10c6fd
--- /dev/null
+++ b/library/alloc/tests/testing/crash_test.rs
@@ -0,0 +1,80 @@
+use std::cmp::Ordering;
+use std::fmt::Debug;
+use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::Ordering::SeqCst;
+
+/// A blueprint for crash test dummy instances that monitor drops.
+/// Some instances may be configured to panic at some point.
+///
+/// Crash test dummies are identified and ordered by an id, so they can be used
+/// as keys in a BTreeMap.
+#[derive(Debug)]
+pub struct CrashTestDummy {
+    pub id: usize,
+    dropped: AtomicUsize,
+}
+
+impl CrashTestDummy {
+    /// Creates a crash test dummy design. The `id` determines order and equality of instances.
+    pub fn new(id: usize) -> CrashTestDummy {
+        CrashTestDummy { id, dropped: AtomicUsize::new(0) }
+    }
+
+    /// Creates an instance of a crash test dummy that records what events it experiences
+    /// and optionally panics.
+    pub fn spawn(&self, panic: Panic) -> Instance<'_> {
+        Instance { origin: self, panic }
+    }
+
+    /// Returns how many times instances of the dummy have been dropped.
+    pub fn dropped(&self) -> usize {
+        self.dropped.load(SeqCst)
+    }
+}
+
+#[derive(Debug)]
+pub struct Instance<'a> {
+    origin: &'a CrashTestDummy,
+    panic: Panic,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Panic {
+    Never,
+    InDrop,
+}
+
+impl Instance<'_> {
+    pub fn id(&self) -> usize {
+        self.origin.id
+    }
+}
+
+impl Drop for Instance<'_> {
+    fn drop(&mut self) {
+        self.origin.dropped.fetch_add(1, SeqCst);
+        if self.panic == Panic::InDrop {
+            panic!("panic in `drop`");
+        }
+    }
+}
+
+impl PartialOrd for Instance<'_> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        self.id().partial_cmp(&other.id())
+    }
+}
+
+impl Ord for Instance<'_> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.id().cmp(&other.id())
+    }
+}
+
+impl PartialEq for Instance<'_> {
+    fn eq(&self, other: &Self) -> bool {
+        self.id().eq(&other.id())
+    }
+}
+
+impl Eq for Instance<'_> {}
diff --git a/library/alloc/tests/testing/mod.rs b/library/alloc/tests/testing/mod.rs
new file mode 100644
index 0000000000000..0a3dd191dc891
--- /dev/null
+++ b/library/alloc/tests/testing/mod.rs
@@ -0,0 +1 @@
+pub mod crash_test;