Improve code quality and add decrypt status return value

tests/romulus-m-reference.test.ts

@@ -1,5 +1,5 @@
 import { referenceTests } from './resources/reference-tests'
-import { cryptoAeadDecrypt, cryptoAeadEncrypt } from '../src/romulus-m'
+import { cryptoAeadDecrypt, cryptoAeadEncrypt, DecryptResult } from '../src/romulus-m'
 
 function parseHexString (string: string): number[] {
   const ret = []
@@ -24,6 +24,9 @@ test.each(referenceTests)('Perform decryption using reference test %#.', (key, n
   const result = cryptoAeadDecrypt(parseHexString(ciphertext), parseHexString(associatedData), parseHexString(nonce), parseHexString(key))
 
   // Then
-  const expectedResult = parseHexString(plaintext)
+  const expectedResult: DecryptResult = {
+    success: true,
+    plaintext: parseHexString(plaintext)
+  }
   expect(result).toMatchObject(expectedResult)
 })