diff --git a/src/libcollections/bit.rs b/src/libcollections/bit.rs
index 953e432fd4a7..ad5732c47a89 100644
--- a/src/libcollections/bit.rs
+++ b/src/libcollections/bit.rs
@@ -2660,7 +2660,7 @@ mod tests {
         s.insert(10);
         s.insert(50);
         s.insert(2);
-        assert_eq!("{1, 2, 10, 50}".to_string(), s.to_string());
+        assert_eq!("{1, 2, 10, 50}", s.to_string());
     }
 
     fn rng() -> rand::IsaacRng {
diff --git a/src/libcollections/btree/set.rs b/src/libcollections/btree/set.rs
index 64ae4f6a5086..bacbe98ad612 100644
--- a/src/libcollections/btree/set.rs
+++ b/src/libcollections/btree/set.rs
@@ -580,7 +580,7 @@ mod test {
 
         let set_str = format!("{}", set);
 
-        assert!(set_str == "{1, 2}".to_string());
-        assert_eq!(format!("{}", empty), "{}".to_string());
+        assert!(set_str == "{1, 2}");
+        assert_eq!(format!("{}", empty), "{}");
     }
 }
diff --git a/src/libcollections/slice.rs b/src/libcollections/slice.rs
index 9417cc3e5947..03b8ea8f20fa 100644
--- a/src/libcollections/slice.rs
+++ b/src/libcollections/slice.rs
@@ -1838,20 +1838,20 @@ mod tests {
             })
         )
         let empty: Vec<int> = vec![];
-        test_show_vec!(empty, "[]".to_string());
-        test_show_vec!(vec![1i], "[1]".to_string());
-        test_show_vec!(vec![1i, 2, 3], "[1, 2, 3]".to_string());
+        test_show_vec!(empty, "[]");
+        test_show_vec!(vec![1i], "[1]");
+        test_show_vec!(vec![1i, 2, 3], "[1, 2, 3]");
         test_show_vec!(vec![vec![], vec![1u], vec![1u, 1u]],
-                       "[[], [1], [1, 1]]".to_string());
+                       "[[], [1], [1, 1]]");
 
         let empty_mut: &mut [int] = &mut[];
-        test_show_vec!(empty_mut, "[]".to_string());
+        test_show_vec!(empty_mut, "[]");
         let v: &mut[int] = &mut[1];
-        test_show_vec!(v, "[1]".to_string());
+        test_show_vec!(v, "[1]");
         let v: &mut[int] = &mut[1, 2, 3];
-        test_show_vec!(v, "[1, 2, 3]".to_string());
+        test_show_vec!(v, "[1, 2, 3]");
         let v: &mut [&mut[uint]] = &mut[&mut[], &mut[1u], &mut[1u, 1u]];
-        test_show_vec!(v, "[[], [1], [1, 1]]".to_string());
+        test_show_vec!(v, "[[], [1], [1, 1]]");
     }
 
     #[test]
diff --git a/src/libcollections/str.rs b/src/libcollections/str.rs
index 6e26962950ba..0c41a850ac3f 100644
--- a/src/libcollections/str.rs
+++ b/src/libcollections/str.rs
@@ -1831,7 +1831,7 @@ mod tests {
     fn test_nfd_chars() {
         macro_rules! t {
             ($input: expr, $expected: expr) => {
-                assert_eq!($input.nfd_chars().collect::<String>(), $expected.into_string());
+                assert_eq!($input.nfd_chars().collect::<String>(), $expected);
             }
         }
         t!("abc", "abc");
@@ -1850,7 +1850,7 @@ mod tests {
     fn test_nfkd_chars() {
         macro_rules! t {
             ($input: expr, $expected: expr) => {
-                assert_eq!($input.nfkd_chars().collect::<String>(), $expected.into_string());
+                assert_eq!($input.nfkd_chars().collect::<String>(), $expected);
             }
         }
         t!("abc", "abc");
@@ -1869,7 +1869,7 @@ mod tests {
     fn test_nfc_chars() {
         macro_rules! t {
             ($input: expr, $expected: expr) => {
-                assert_eq!($input.nfc_chars().collect::<String>(), $expected.into_string());
+                assert_eq!($input.nfc_chars().collect::<String>(), $expected);
             }
         }
         t!("abc", "abc");
@@ -1889,7 +1889,7 @@ mod tests {
     fn test_nfkc_chars() {
         macro_rules! t {
             ($input: expr, $expected: expr) => {
-                assert_eq!($input.nfkc_chars().collect::<String>(), $expected.into_string());
+                assert_eq!($input.nfkc_chars().collect::<String>(), $expected);
             }
         }
         t!("abc", "abc");
diff --git a/src/libcollections/string.rs b/src/libcollections/string.rs
index a7545d069602..571f3fa46858 100644
--- a/src/libcollections/string.rs
+++ b/src/libcollections/string.rs
@@ -1287,24 +1287,24 @@ mod tests {
 
     #[test]
     fn test_simple_types() {
-        assert_eq!(1i.to_string(), "1".to_string());
-        assert_eq!((-1i).to_string(), "-1".to_string());
-        assert_eq!(200u.to_string(), "200".to_string());
-        assert_eq!(2u8.to_string(), "2".to_string());
-        assert_eq!(true.to_string(), "true".to_string());
-        assert_eq!(false.to_string(), "false".to_string());
-        assert_eq!(().to_string(), "()".to_string());
-        assert_eq!(("hi".to_string()).to_string(), "hi".to_string());
+        assert_eq!(1i.to_string(), "1");
+        assert_eq!((-1i).to_string(), "-1");
+        assert_eq!(200u.to_string(), "200");
+        assert_eq!(2u8.to_string(), "2");
+        assert_eq!(true.to_string(), "true");
+        assert_eq!(false.to_string(), "false");
+        assert_eq!(().to_string(), "()");
+        assert_eq!(("hi".to_string()).to_string(), "hi");
     }
 
     #[test]
     fn test_vectors() {
         let x: Vec<int> = vec![];
-        assert_eq!(x.to_string(), "[]".to_string());
-        assert_eq!((vec![1i]).to_string(), "[1]".to_string());
-        assert_eq!((vec![1i, 2, 3]).to_string(), "[1, 2, 3]".to_string());
+        assert_eq!(x.to_string(), "[]");
+        assert_eq!((vec![1i]).to_string(), "[1]");
+        assert_eq!((vec![1i, 2, 3]).to_string(), "[1, 2, 3]");
         assert!((vec![vec![], vec![1i], vec![1i, 1]]).to_string() ==
-               "[[], [1], [1, 1]]".to_string());
+               "[[], [1], [1, 1]]");
     }
 
     #[bench]
diff --git a/src/libcollections/tree/map.rs b/src/libcollections/tree/map.rs
index 119268c27eea..3818be5a1979 100644
--- a/src/libcollections/tree/map.rs
+++ b/src/libcollections/tree/map.rs
@@ -1735,8 +1735,8 @@ mod test_treemap {
 
         let map_str = format!("{}", map);
 
-        assert!(map_str == "{1: 2, 3: 4}".to_string());
-        assert_eq!(format!("{}", empty), "{}".to_string());
+        assert!(map_str == "{1: 2, 3: 4}");
+        assert_eq!(format!("{}", empty), "{}");
     }
 
     #[test]
diff --git a/src/libcollections/tree/set.rs b/src/libcollections/tree/set.rs
index 6988b929df68..bdb33f704991 100644
--- a/src/libcollections/tree/set.rs
+++ b/src/libcollections/tree/set.rs
@@ -979,7 +979,7 @@ mod test {
 
         let set_str = format!("{}", set);
 
-        assert!(set_str == "{1, 2}".to_string());
-        assert_eq!(format!("{}", empty), "{}".to_string());
+        assert!(set_str == "{1, 2}");
+        assert_eq!(format!("{}", empty), "{}");
     }
 }
diff --git a/src/libcollections/trie/map.rs b/src/libcollections/trie/map.rs
index 672ddab4d87e..6491c9a569dc 100644
--- a/src/libcollections/trie/map.rs
+++ b/src/libcollections/trie/map.rs
@@ -1605,8 +1605,8 @@ mod test {
 
         let map_str = format!("{}", map);
 
-        assert!(map_str == "{1: a, 2: b}".to_string());
-        assert_eq!(format!("{}", empty), "{}".to_string());
+        assert!(map_str == "{1: a, 2: b}");
+        assert_eq!(format!("{}", empty), "{}");
     }
 
     #[test]
diff --git a/src/libcollections/trie/set.rs b/src/libcollections/trie/set.rs
index 1b3657943da6..436da5117428 100644
--- a/src/libcollections/trie/set.rs
+++ b/src/libcollections/trie/set.rs
@@ -696,8 +696,8 @@ mod test {
 
         let set_str = format!("{}", set);
 
-        assert!(set_str == "{1, 2}".to_string());
-        assert_eq!(format!("{}", empty), "{}".to_string());
+        assert!(set_str == "{1, 2}");
+        assert_eq!(format!("{}", empty), "{}");
     }
 
     #[test]
diff --git a/src/libcollections/vec_map.rs b/src/libcollections/vec_map.rs
index 3be662c071c1..97b80108d766 100644
--- a/src/libcollections/vec_map.rs
+++ b/src/libcollections/vec_map.rs
@@ -871,7 +871,7 @@ mod test_map {
 
         let map_str = map.to_string();
         assert!(map_str == "{1: 2, 3: 4}" || map_str == "{3: 4, 1: 2}");
-        assert_eq!(format!("{}", empty), "{}".to_string());
+        assert_eq!(format!("{}", empty), "{}");
     }
 
     #[test]