diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs
index 86cf6fc104c8..36476cf01c08 100644
--- a/src/libcore/tests/lib.rs
+++ b/src/libcore/tests/lib.rs
@@ -41,6 +41,7 @@
 #![feature(const_raw_ptr_deref)]
 #![feature(never_type)]
 #![feature(unwrap_infallible)]
+#![feature(leading_trailing_ones)]
 
 extern crate test;
 
diff --git a/src/libcore/tests/num/int_macros.rs b/src/libcore/tests/num/int_macros.rs
index 4a44b5f24b91..48a49073b2cf 100644
--- a/src/libcore/tests/num/int_macros.rs
+++ b/src/libcore/tests/num/int_macros.rs
@@ -89,6 +89,33 @@ macro_rules! int_module {
                 assert_eq!(C.count_zeros(), bits as u32 - 5);
             }
 
+            #[test]
+            fn test_leading_trailing_ones() {
+                let bits = (mem::size_of::<$T>() * 8) as u32;
+
+                let a: $T = 0b0101_1111;
+                assert_eq!(a.trailing_ones(), 5);
+                assert_eq!((!a).leading_ones(), bits - 7);
+
+                assert_eq!(a.reverse_bits().leading_ones(), 5);
+
+                assert_eq!(_1.leading_ones(), bits);
+                assert_eq!(_1.trailing_ones(), bits);
+
+                assert_eq!((_1 << 1).trailing_ones(), 0);
+                assert_eq!(MAX.leading_ones(), 0);
+
+                assert_eq!((_1 << 1).leading_ones(), bits - 1);
+                assert_eq!(MAX.trailing_ones(), bits - 1);
+
+                assert_eq!(_0.leading_ones(), 0);
+                assert_eq!(_0.trailing_ones(), 0);
+
+                let x: $T = 0b0010_1100;
+                assert_eq!(x.leading_ones(), 0);
+                assert_eq!(x.trailing_ones(), 0);
+            }
+
             #[test]
             fn test_rotate() {
                 assert_eq!(A.rotate_left(6).rotate_right(2).rotate_right(4), A);
diff --git a/src/libcore/tests/num/uint_macros.rs b/src/libcore/tests/num/uint_macros.rs
index f94b2f56bbbe..8f1ca8e6fac2 100644
--- a/src/libcore/tests/num/uint_macros.rs
+++ b/src/libcore/tests/num/uint_macros.rs
@@ -53,6 +53,33 @@ macro_rules! uint_module {
                 assert!(C.count_zeros() == bits as u32 - 5);
             }
 
+            #[test]
+            fn test_leading_trailing_ones() {
+                let bits = (mem::size_of::<$T>() * 8) as u32;
+
+                let a: $T = 0b0101_1111;
+                assert_eq!(a.trailing_ones(), 5);
+                assert_eq!((!a).leading_ones(), bits - 7);
+
+                assert_eq!(a.reverse_bits().leading_ones(), 5);
+
+                assert_eq!(_1.leading_ones(), bits);
+                assert_eq!(_1.trailing_ones(), bits);
+
+                assert_eq!((_1 << 1).trailing_ones(), 0);
+                assert_eq!((_1 >> 1).leading_ones(), 0);
+
+                assert_eq!((_1 << 1).leading_ones(), bits - 1);
+                assert_eq!((_1 >> 1).trailing_ones(), bits - 1);
+
+                assert_eq!(_0.leading_ones(), 0);
+                assert_eq!(_0.trailing_ones(), 0);
+
+                let x: $T = 0b0010_1100;
+                assert_eq!(x.leading_ones(), 0);
+                assert_eq!(x.trailing_ones(), 0);
+            }
+
             #[test]
             fn test_rotate() {
                 assert_eq!(A.rotate_left(6).rotate_right(2).rotate_right(4), A);