digest: add dev::initialized_mac_test function (#2367)

Author: SalusaSecondus

digest/CHANGELOG.md

@@ -5,6 +5,12 @@ 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).
 
+## 0.11.3 (UNRELEASED)
+### Added
+- `dev::initialized_mac_test` function ([#2367])
+
+[#2367]: https://github.com/RustCrypto/traits/pull/2367
+
 ## 0.11.2 (2026-03-13)
 ### Changed
 - Do not implement `Clone` as part of `(Reset)MacTraits` in the `buffer_fixed!` macro ([#2341])

digest/src/dev/mac.rs

@@ -31,6 +31,17 @@ pub fn mac_test<M: Mac + KeyInit + Clone>(
         return Err("Failed to initialize MAC instance");
     };
 
+    initialized_mac_test(mac0, input, tag, trunc_side)
+}
+
+/// Run the MAC test directly on an initialized MAC.
+/// This is useful for when custom initialization is needed
+pub fn initialized_mac_test<M: Mac + Clone>(
+    mac0: M,
+    input: &[u8],
+    tag: &[u8],
+    trunc_side: MacTruncSide,
+) -> Result<(), &'static str> {
     let mut mac = mac0.clone();
     mac.update(input);
     let result = mac.finalize().into_bytes();