added tests

crates/crypto/src/lib.rs

@@ -63,4 +63,39 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn helper_generates_expected_sizes() {
+        let key = helper::gen_key();
+        let nonce = helper::gen_nonce();
+
+        assert_eq!(key.as_slice().len(), 32);
+        assert_eq!(nonce.as_slice().len(), 12);
+    }
+
+    #[test]
+    fn key_from_validates_length() {
+        let key = helper::key_from(vec![7u8; 32]).expect("expected valid key");
+        assert_eq!(key.as_slice(), vec![7u8; 32]);
+
+        let err = helper::key_from(vec![1u8; 31]).unwrap_err();
+        assert_eq!(err.to_string(), "key must be exactly 32 bytes");
+    }
+
+    #[test]
+    fn decrypt_fails_with_wrong_key_or_tampered_ciphertext() {
+        let key = helper::gen_key();
+        let other_key = helper::gen_key();
+        let plaintext = b"secret".to_vec();
+
+        let (nonce, mut ciphertext) = encrypt(&key, plaintext.clone()).expect("encrypt");
+
+        assert!(decrypt(&other_key, ciphertext.clone(), &nonce).is_err());
+
+        if let Some(byte) = ciphertext.get_mut(0) {
+            *byte ^= 0b1010_1010;
+        }
+
+        assert!(decrypt(&key, ciphertext, &nonce).is_err());
+    }
 }