diff --git a/src/string.rs b/src/string.rs
index 4b4f7619..faec39e1 100644
--- a/src/string.rs
+++ b/src/string.rs
@@ -494,6 +494,22 @@ mod tests {
         assert_eq!(s2, "abcd efgh");
     }
 
+    #[test]
+    fn cmp() {
+        let s1: String<4> = String::from("abcd");
+        let s2: String<4> = String::from("zzzz");
+
+        assert!(s1 < s2);
+    }
+
+    #[test]
+    fn cmp_heterogenous_size() {
+        let s1: String<4> = String::from("abcd");
+        let s2: String<8> = String::from("zzzz");
+
+        assert!(s1 < s2);
+    }
+
     #[test]
     fn debug() {
         use core::fmt::Write;
diff --git a/src/vec.rs b/src/vec.rs
index 5143003f..73c160c6 100644
--- a/src/vec.rs
+++ b/src/vec.rs
@@ -907,6 +907,32 @@ mod tests {
         assert_eq!(xs, ys);
     }
 
+    #[test]
+    fn cmp() {
+        let mut xs: Vec<i32, 4> = Vec::new();
+        let mut ys: Vec<i32, 4> = Vec::new();
+
+        assert_eq!(xs, ys);
+
+        xs.push(1).unwrap();
+        ys.push(2).unwrap();
+
+        assert!(xs < ys);
+    }
+
+    #[test]
+    fn cmp_heterogenous_size() {
+        let mut xs: Vec<i32, 4> = Vec::new();
+        let mut ys: Vec<i32, 8> = Vec::new();
+
+        assert_eq!(xs, ys);
+
+        xs.push(1).unwrap();
+        ys.push(2).unwrap();
+
+        assert!(xs < ys);
+    }
+
     #[test]
     fn full() {
         let mut v: Vec<i32, 4> = Vec::new();