diff --git a/src/libextra/num/bigint.rs b/src/libextra/num/bigint.rs
index 00eec3e9ac44..6e2a6fcbfeea 100644
--- a/src/libextra/num/bigint.rs
+++ b/src/libextra/num/bigint.rs
@@ -1167,83 +1167,78 @@ mod biguint_tests {
 
     #[test]
     fn test_shl() {
-        fn check(v: ~[BigDigit], shift: uint, ans: ~[BigDigit]) {
-            assert_eq!(BigUint::new(v) << shift, BigUint::new(ans));
+        fn check(s: &str, shift: uint, ans: &str) {
+            let bu = (FromStrRadix::from_str_radix::<BigUint>(s, 16).unwrap() << shift)
+                .to_str_radix(16);
+            assert_eq!(bu.as_slice(), ans);
         }
 
-        check(~[], 3, ~[]);
-        check(~[1, 1, 1], 3, ~[1 << 3, 1 << 3, 1 << 3]);
-        check(~[1 << (BigDigit::bits - 2)], 2, ~[0, 1]);
-        check(~[1 << (BigDigit::bits - 2)], 3, ~[0, 2]);
-        check(~[1 << (BigDigit::bits - 2)], 3 + BigDigit::bits, ~[0, 0, 2]);
+        check("0", 3, "0");
+        check("1", 3, "8");
 
-        test_shl_bits();
+        check("1" + "0000" + "0000" + "0000" + "0001" + "0000" + "0000" + "0000" + "0001", 3,
+              "8" + "0000" + "0000" + "0000" + "0008" + "0000" + "0000" + "0000" + "0008");
+        check("1" + "0000" + "0001" + "0000" + "0001", 2,
+              "4" + "0000" + "0004" + "0000" + "0004");
+        check("1" + "0001" + "0001", 1,
+              "2" + "0002" + "0002");
 
-        #[cfg(target_word_size = "64")]
-        fn test_shl_bits() {
-            check(~[0x7654_3210, 0xfedc_ba98,
-                    0x7654_3210, 0xfedc_ba98], 4,
-                  ~[0x6543_2100, 0xedcb_a987,
-                    0x6543_210f, 0xedcb_a987, 0xf]);
-            check(~[0x2222_1111, 0x4444_3333,
-                    0x6666_5555, 0x8888_7777], 16,
-                  ~[0x1111_0000, 0x3333_2222,
-                    0x5555_4444, 0x7777_6666, 0x8888]);
-        }
+        check(""  + "4000" + "0000" + "0000" + "0000", 3,
+              "2" + "0000" + "0000" + "0000" + "0000");
+        check(""  + "4000" + "0000", 2,
+              "1" + "0000" + "0000");
+        check(""  + "4000", 2,
+              "1" + "0000");
 
-        #[cfg(target_word_size = "32")]
-        fn test_shl_bits() {
-            check(~[0x3210, 0x7654, 0xba98, 0xfedc,
-                    0x3210, 0x7654, 0xba98, 0xfedc], 4,
-                  ~[0x2100, 0x6543, 0xa987, 0xedcb,
-                    0x210f, 0x6543, 0xa987, 0xedcb, 0xf]);
-            check(~[0x1111, 0x2222, 0x3333, 0x4444,
-                    0x5555, 0x6666, 0x7777, 0x8888], 16,
-                  ~[0x0000, 0x1111, 0x2222, 0x3333,
-                    0x4444, 0x5555, 0x6666, 0x7777, 0x8888]);
-        }
+        check(""  + "4000" + "0000" + "0000" + "0000", 67,
+              "2" + "0000" + "0000" + "0000" + "0000" + "0000" + "0000" + "0000" + "0000");
+        check(""  + "4000" + "0000", 35,
+              "2" + "0000" + "0000" + "0000" + "0000");
+        check(""  + "4000", 19,
+              "2" + "0000" + "0000");
 
+        check(""  + "fedc" + "ba98" + "7654" + "3210" + "fedc" + "ba98" + "7654" + "3210", 4,
+              "f" + "edcb" + "a987" + "6543" + "210f" + "edcb" + "a987" + "6543" + "2100");
+        check("88887777666655554444333322221111", 16,
+              "888877776666555544443333222211110000");
     }
 
     #[test]
-    #[ignore(cfg(target_word_size = "32"))]
     fn test_shr() {
-        fn check(v: ~[BigDigit], shift: uint, ans: ~[BigDigit]) {
-            assert_eq!(BigUint::new(v) >> shift, BigUint::new(ans));
+        fn check(s: &str, shift: uint, ans: &str) {
+            let bu = (FromStrRadix::from_str_radix::<BigUint>(s, 16).unwrap() >> shift)
+                .to_str_radix(16);
+            assert_eq!(bu.as_slice(), ans);
         }
 
-        check(~[], 3, ~[]);
-        check(~[1, 1, 1], 3,
-              ~[1 << (BigDigit::bits - 3), 1 << (BigDigit::bits - 3)]);
-        check(~[1 << 2], 2, ~[1]);
-        check(~[1, 2], 3, ~[1 << (BigDigit::bits - 2)]);
-        check(~[1, 1, 2], 3 + BigDigit::bits, ~[1 << (BigDigit::bits - 2)]);
-        check(~[0, 1], 1, ~[0x80000000]);
-        test_shr_bits();
+        check("0", 3, "0");
+        check("f", 3, "1");
 
-        #[cfg(target_word_size = "64")]
-        fn test_shr_bits() {
-            check(~[0x6543_2100, 0xedcb_a987,
-                    0x6543_210f, 0xedcb_a987, 0xf], 4,
-                  ~[0x7654_3210, 0xfedc_ba98,
-                    0x7654_3210, 0xfedc_ba98]);
-            check(~[0x1111_0000, 0x3333_2222,
-                    0x5555_4444, 0x7777_6666, 0x8888], 16,
-                  ~[0x2222_1111, 0x4444_3333,
-                    0x6666_5555, 0x8888_7777]);
-        }
+        check("1" + "0000" + "0000" + "0000" + "0001" + "0000" + "0000" + "0000" + "0001", 3,
+              ""  + "2000" + "0000" + "0000" + "0000" + "2000" + "0000" + "0000" + "0000");
+        check("1" + "0000" + "0001" + "0000" + "0001", 2,
+              ""  + "4000" + "0000" + "4000" + "0000");
+        check("1" + "0001" + "0001", 1,
+              ""  + "8000" + "8000");
 
-        #[cfg(target_word_size = "32")]
-        fn test_shr_bits() {
-            check(~[0x2100, 0x6543, 0xa987, 0xedcb,
-                    0x210f, 0x6543, 0xa987, 0xedcb, 0xf], 4,
-                  ~[0x3210, 0x7654, 0xba98, 0xfedc,
-                    0x3210, 0x7654, 0xba98, 0xfedc]);
-            check(~[0x0000, 0x1111, 0x2222, 0x3333,
-                    0x4444, 0x5555, 0x6666, 0x7777, 0x8888], 16,
-                  ~[0x1111, 0x2222, 0x3333, 0x4444,
-                    0x5555, 0x6666, 0x7777, 0x8888]);
-        }
+        check("2" + "0000" + "0000" + "0000" + "0001" + "0000" + "0000" + "0000" + "0001", 67,
+              ""  + "4000" + "0000" + "0000" + "0000");
+        check("2" + "0000" + "0001" + "0000" + "0001", 35,
+              ""  + "4000" + "0000");
+        check("2" + "0001" + "0001", 19,
+              ""  + "4000");
+
+        check("1" + "0000" + "0000" + "0000" + "0000", 1,
+              ""  + "8000" + "0000" + "0000" + "0000");
+        check("1" + "0000" + "0000", 1,
+              ""  + "8000" + "0000");
+        check("1" + "0000", 1,
+              ""  + "8000");
+        check("f" + "edcb" + "a987" + "6543" + "210f" + "edcb" + "a987" + "6543" + "2100", 4,
+              ""  + "fedc" + "ba98" + "7654" + "3210" + "fedc" + "ba98" + "7654" + "3210");
+
+        check("888877776666555544443333222211110000", 16,
+              "88887777666655554444333322221111");
     }
 
     #[test]