diff --git a/src/libarena/lib.rs b/src/libarena/lib.rs
index 1739b2236e8..e2a249c8e61 100644
--- a/src/libarena/lib.rs
+++ b/src/libarena/lib.rs
@@ -617,218 +617,4 @@ impl SyncDroplessArena {
 }
 
 #[cfg(test)]
-mod tests {
-    extern crate test;
-    use test::Bencher;
-    use super::TypedArena;
-    use std::cell::Cell;
-
-    #[allow(dead_code)]
-    #[derive(Debug, Eq, PartialEq)]
-    struct Point {
-        x: i32,
-        y: i32,
-        z: i32,
-    }
-
-    #[test]
-    pub fn test_unused() {
-        let arena: TypedArena<Point> = TypedArena::default();
-        assert!(arena.chunks.borrow().is_empty());
-    }
-
-    #[test]
-    fn test_arena_alloc_nested() {
-        struct Inner {
-            value: u8,
-        }
-        struct Outer<'a> {
-            inner: &'a Inner,
-        }
-        enum EI<'e> {
-            I(Inner),
-            O(Outer<'e>),
-        }
-
-        struct Wrap<'a>(TypedArena<EI<'a>>);
-
-        impl<'a> Wrap<'a> {
-            fn alloc_inner<F: Fn() -> Inner>(&self, f: F) -> &Inner {
-                let r: &EI<'_> = self.0.alloc(EI::I(f()));
-                if let &EI::I(ref i) = r {
-                    i
-                } else {
-                    panic!("mismatch");
-                }
-            }
-            fn alloc_outer<F: Fn() -> Outer<'a>>(&self, f: F) -> &Outer<'_> {
-                let r: &EI<'_> = self.0.alloc(EI::O(f()));
-                if let &EI::O(ref o) = r {
-                    o
-                } else {
-                    panic!("mismatch");
-                }
-            }
-        }
-
-        let arena = Wrap(TypedArena::default());
-
-        let result = arena.alloc_outer(|| Outer {
-            inner: arena.alloc_inner(|| Inner { value: 10 }),
-        });
-
-        assert_eq!(result.inner.value, 10);
-    }
-
-    #[test]
-    pub fn test_copy() {
-        let arena = TypedArena::default();
-        for _ in 0..100000 {
-            arena.alloc(Point { x: 1, y: 2, z: 3 });
-        }
-    }
-
-    #[bench]
-    pub fn bench_copy(b: &mut Bencher) {
-        let arena = TypedArena::default();
-        b.iter(|| arena.alloc(Point { x: 1, y: 2, z: 3 }))
-    }
-
-    #[bench]
-    pub fn bench_copy_nonarena(b: &mut Bencher) {
-        b.iter(|| {
-            let _: Box<_> = Box::new(Point { x: 1, y: 2, z: 3 });
-        })
-    }
-
-    #[allow(dead_code)]
-    struct Noncopy {
-        string: String,
-        array: Vec<i32>,
-    }
-
-    #[test]
-    pub fn test_noncopy() {
-        let arena = TypedArena::default();
-        for _ in 0..100000 {
-            arena.alloc(Noncopy {
-                string: "hello world".to_string(),
-                array: vec![1, 2, 3, 4, 5],
-            });
-        }
-    }
-
-    #[test]
-    pub fn test_typed_arena_zero_sized() {
-        let arena = TypedArena::default();
-        for _ in 0..100000 {
-            arena.alloc(());
-        }
-    }
-
-    #[test]
-    pub fn test_typed_arena_clear() {
-        let mut arena = TypedArena::default();
-        for _ in 0..10 {
-            arena.clear();
-            for _ in 0..10000 {
-                arena.alloc(Point { x: 1, y: 2, z: 3 });
-            }
-        }
-    }
-
-    #[bench]
-    pub fn bench_typed_arena_clear(b: &mut Bencher) {
-        let mut arena = TypedArena::default();
-        b.iter(|| {
-            arena.alloc(Point { x: 1, y: 2, z: 3 });
-            arena.clear();
-        })
-    }
-
-    // Drop tests
-
-    struct DropCounter<'a> {
-        count: &'a Cell<u32>,
-    }
-
-    impl Drop for DropCounter<'_> {
-        fn drop(&mut self) {
-            self.count.set(self.count.get() + 1);
-        }
-    }
-
-    #[test]
-    fn test_typed_arena_drop_count() {
-        let counter = Cell::new(0);
-        {
-            let arena: TypedArena<DropCounter<'_>> = TypedArena::default();
-            for _ in 0..100 {
-                // Allocate something with drop glue to make sure it doesn't leak.
-                arena.alloc(DropCounter { count: &counter });
-            }
-        };
-        assert_eq!(counter.get(), 100);
-    }
-
-    #[test]
-    fn test_typed_arena_drop_on_clear() {
-        let counter = Cell::new(0);
-        let mut arena: TypedArena<DropCounter<'_>> = TypedArena::default();
-        for i in 0..10 {
-            for _ in 0..100 {
-                // Allocate something with drop glue to make sure it doesn't leak.
-                arena.alloc(DropCounter { count: &counter });
-            }
-            arena.clear();
-            assert_eq!(counter.get(), i * 100 + 100);
-        }
-    }
-
-    thread_local! {
-        static DROP_COUNTER: Cell<u32> = Cell::new(0)
-    }
-
-    struct SmallDroppable;
-
-    impl Drop for SmallDroppable {
-        fn drop(&mut self) {
-            DROP_COUNTER.with(|c| c.set(c.get() + 1));
-        }
-    }
-
-    #[test]
-    fn test_typed_arena_drop_small_count() {
-        DROP_COUNTER.with(|c| c.set(0));
-        {
-            let arena: TypedArena<SmallDroppable> = TypedArena::default();
-            for _ in 0..100 {
-                // Allocate something with drop glue to make sure it doesn't leak.
-                arena.alloc(SmallDroppable);
-            }
-            // dropping
-        };
-        assert_eq!(DROP_COUNTER.with(|c| c.get()), 100);
-    }
-
-    #[bench]
-    pub fn bench_noncopy(b: &mut Bencher) {
-        let arena = TypedArena::default();
-        b.iter(|| {
-            arena.alloc(Noncopy {
-                string: "hello world".to_string(),
-                array: vec![1, 2, 3, 4, 5],
-            })
-        })
-    }
-
-    #[bench]
-    pub fn bench_noncopy_nonarena(b: &mut Bencher) {
-        b.iter(|| {
-            let _: Box<_> = Box::new(Noncopy {
-                string: "hello world".to_string(),
-                array: vec![1, 2, 3, 4, 5],
-            });
-        })
-    }
-}
+mod tests;
diff --git a/src/libarena/tests.rs b/src/libarena/tests.rs
new file mode 100644
index 00000000000..fa4189409d0
--- /dev/null
+++ b/src/libarena/tests.rs
@@ -0,0 +1,213 @@
+extern crate test;
+use test::Bencher;
+use super::TypedArena;
+use std::cell::Cell;
+
+#[allow(dead_code)]
+#[derive(Debug, Eq, PartialEq)]
+struct Point {
+    x: i32,
+    y: i32,
+    z: i32,
+}
+
+#[test]
+pub fn test_unused() {
+    let arena: TypedArena<Point> = TypedArena::default();
+    assert!(arena.chunks.borrow().is_empty());
+}
+
+#[test]
+fn test_arena_alloc_nested() {
+    struct Inner {
+        value: u8,
+    }
+    struct Outer<'a> {
+        inner: &'a Inner,
+    }
+    enum EI<'e> {
+        I(Inner),
+        O(Outer<'e>),
+    }
+
+    struct Wrap<'a>(TypedArena<EI<'a>>);
+
+    impl<'a> Wrap<'a> {
+        fn alloc_inner<F: Fn() -> Inner>(&self, f: F) -> &Inner {
+            let r: &EI<'_> = self.0.alloc(EI::I(f()));
+            if let &EI::I(ref i) = r {
+                i
+            } else {
+                panic!("mismatch");
+            }
+        }
+        fn alloc_outer<F: Fn() -> Outer<'a>>(&self, f: F) -> &Outer<'_> {
+            let r: &EI<'_> = self.0.alloc(EI::O(f()));
+            if let &EI::O(ref o) = r {
+                o
+            } else {
+                panic!("mismatch");
+            }
+        }
+    }
+
+    let arena = Wrap(TypedArena::default());
+
+    let result = arena.alloc_outer(|| Outer {
+        inner: arena.alloc_inner(|| Inner { value: 10 }),
+    });
+
+    assert_eq!(result.inner.value, 10);
+}
+
+#[test]
+pub fn test_copy() {
+    let arena = TypedArena::default();
+    for _ in 0..100000 {
+        arena.alloc(Point { x: 1, y: 2, z: 3 });
+    }
+}
+
+#[bench]
+pub fn bench_copy(b: &mut Bencher) {
+    let arena = TypedArena::default();
+    b.iter(|| arena.alloc(Point { x: 1, y: 2, z: 3 }))
+}
+
+#[bench]
+pub fn bench_copy_nonarena(b: &mut Bencher) {
+    b.iter(|| {
+        let _: Box<_> = Box::new(Point { x: 1, y: 2, z: 3 });
+    })
+}
+
+#[allow(dead_code)]
+struct Noncopy {
+    string: String,
+    array: Vec<i32>,
+}
+
+#[test]
+pub fn test_noncopy() {
+    let arena = TypedArena::default();
+    for _ in 0..100000 {
+        arena.alloc(Noncopy {
+            string: "hello world".to_string(),
+            array: vec![1, 2, 3, 4, 5],
+        });
+    }
+}
+
+#[test]
+pub fn test_typed_arena_zero_sized() {
+    let arena = TypedArena::default();
+    for _ in 0..100000 {
+        arena.alloc(());
+    }
+}
+
+#[test]
+pub fn test_typed_arena_clear() {
+    let mut arena = TypedArena::default();
+    for _ in 0..10 {
+        arena.clear();
+        for _ in 0..10000 {
+            arena.alloc(Point { x: 1, y: 2, z: 3 });
+        }
+    }
+}
+
+#[bench]
+pub fn bench_typed_arena_clear(b: &mut Bencher) {
+    let mut arena = TypedArena::default();
+    b.iter(|| {
+        arena.alloc(Point { x: 1, y: 2, z: 3 });
+        arena.clear();
+    })
+}
+
+// Drop tests
+
+struct DropCounter<'a> {
+    count: &'a Cell<u32>,
+}
+
+impl Drop for DropCounter<'_> {
+    fn drop(&mut self) {
+        self.count.set(self.count.get() + 1);
+    }
+}
+
+#[test]
+fn test_typed_arena_drop_count() {
+    let counter = Cell::new(0);
+    {
+        let arena: TypedArena<DropCounter<'_>> = TypedArena::default();
+        for _ in 0..100 {
+            // Allocate something with drop glue to make sure it doesn't leak.
+            arena.alloc(DropCounter { count: &counter });
+        }
+    };
+    assert_eq!(counter.get(), 100);
+}
+
+#[test]
+fn test_typed_arena_drop_on_clear() {
+    let counter = Cell::new(0);
+    let mut arena: TypedArena<DropCounter<'_>> = TypedArena::default();
+    for i in 0..10 {
+        for _ in 0..100 {
+            // Allocate something with drop glue to make sure it doesn't leak.
+            arena.alloc(DropCounter { count: &counter });
+        }
+        arena.clear();
+        assert_eq!(counter.get(), i * 100 + 100);
+    }
+}
+
+thread_local! {
+    static DROP_COUNTER: Cell<u32> = Cell::new(0)
+}
+
+struct SmallDroppable;
+
+impl Drop for SmallDroppable {
+    fn drop(&mut self) {
+        DROP_COUNTER.with(|c| c.set(c.get() + 1));
+    }
+}
+
+#[test]
+fn test_typed_arena_drop_small_count() {
+    DROP_COUNTER.with(|c| c.set(0));
+    {
+        let arena: TypedArena<SmallDroppable> = TypedArena::default();
+        for _ in 0..100 {
+            // Allocate something with drop glue to make sure it doesn't leak.
+            arena.alloc(SmallDroppable);
+        }
+        // dropping
+    };
+    assert_eq!(DROP_COUNTER.with(|c| c.get()), 100);
+}
+
+#[bench]
+pub fn bench_noncopy(b: &mut Bencher) {
+    let arena = TypedArena::default();
+    b.iter(|| {
+        arena.alloc(Noncopy {
+            string: "hello world".to_string(),
+            array: vec![1, 2, 3, 4, 5],
+        })
+    })
+}
+
+#[bench]
+pub fn bench_noncopy_nonarena(b: &mut Bencher) {
+    b.iter(|| {
+        let _: Box<_> = Box::new(Noncopy {
+            string: "hello world".to_string(),
+            array: vec![1, 2, 3, 4, 5],
+        });
+    })
+}