test(cipher): Add mutation tests

Relates to: matrix-org#78

Signed-off-by: Johannes Marbach <[email protected]>

.cargo/mutants.toml

@@ -12,6 +12,8 @@ exclude_re = [
  # These cause olm/account tests to hang
  "RemoteChainKey::chain_index",
  "RemoteChainKey::advance",
+ # Intentionally returns Ok(()) in all cases
+ "replace Cipher::verify_truncated_mac -> Result<\\(\\), MacError> with Ok\\(\\(\\)\\)",
  # The constant value can't really be tested
  "src/olm/account/one_time_keys\\.rs.*replace \\* with \\+$",
 ]

src/cipher/mod.rs

@@ -192,3 +192,18 @@ impl Cipher {
  Ok(())
  }
 }
+
+#[cfg(test)]
+mod test {
+ use super::{Cipher, Mac};
+ use crate::cipher::DecryptionError;
+
+ #[test]
+ fn decrypt_pickle_mac_missing() {
+ let cipher = Cipher::new(&[1u8; 32]);
+ assert!(matches!(
+ cipher.decrypt_pickle(&[2u8; Mac::TRUNCATED_LEN]),
+ Err(DecryptionError::MacMissing)
+ ));
+ }
+}