update changelog and add a couple tests

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+-   Adds unsafe associated methods `Pointer::new_unchecked` and `PointerBuf::new_unchecked` for
+    external zero-cost construction.
+
 ## [0.6.2] 2024-09-30
 
 ### Added

src/pointer.rs

@@ -51,7 +51,7 @@ impl core::fmt::Display for Pointer {
 impl Pointer {
     /// Create a `Pointer` from a string that is known to be correctly encoded.
     ///
-    /// This is a zero-copy constructor.
+    /// This is a cost-free conversion.
     ///
     /// ## Safety
     /// The provided string must adhere to RFC 6901.
@@ -1302,6 +1302,20 @@ mod tests {
         let _ = Pointer::from_static("foo/bar");
     }
 
+    #[test]
+    fn root_is_alias_of_new_pathbuf() {
+        assert_eq!(PointerBuf::root(), PointerBuf::new());
+    }
+
+    #[test]
+    fn from_unchecked_pathbuf() {
+        let s = "/foo/bar/0";
+        assert_eq!(
+            unsafe { PointerBuf::new_unchecked(String::from(s)) },
+            PointerBuf::parse(s).unwrap()
+        );
+    }
+
     #[test]
     fn strip_suffix() {
         let p = Pointer::from_static("/example/pointer/to/some/value");