digest: add hash_serialization_test macro

digest/src/dev.rs

@@ -38,6 +38,40 @@ macro_rules! new_test {
     };
 }
 
+/// Define hash function serialization test
+#[macro_export]
+#[cfg_attr(docsrs, doc(cfg(feature = "dev")))]
+macro_rules! hash_serialization_test {
+    ($name:ident, $hasher:ty, $expected_serialized_state:expr) => {
+        #[test]
+        fn $name() {
+            use digest::{
+                crypto_common::{BlockSizeUser, SerializableState},
+                typenum::Unsigned,
+                Digest,
+            };
+
+            let mut h = <$hasher>::new();
+
+            h.update(&[0x13; <$hasher as BlockSizeUser>::BlockSize::USIZE + 1]);
+
+            let serialized_state = h.serialize();
+            assert_eq!(serialized_state.as_slice(), $expected_serialized_state);
+
+            let mut h = <$hasher>::deserialize(&serialized_state).unwrap();
+
+            h.update(&[0x13; <$hasher as BlockSizeUser>::BlockSize::USIZE + 1]);
+            let output1 = h.finalize();
+
+            let mut h = <$hasher>::new();
+            h.update(&[0x13; 2 * (<$hasher as BlockSizeUser>::BlockSize::USIZE + 1)]);
+            let output2 = h.finalize();
+
+            assert_eq!(output1, output2);
+        }
+    };
+}
+
 /// Define [`Update`][crate::Update] impl benchmark
 #[macro_export]
 macro_rules! bench_update {