More of a storage_index_hash test

src/allmydata/test/test_hashutil.py

@@ -102,9 +102,35 @@ class HashUtilTests(unittest.TestCase):
         got_a = base32.b2a(got)
         self.failUnlessEqual(got_a, expected_a)
 
-    def test_known_answers(self):
-        # assert backwards compatibility
+    def test_storage_index_hash_known_answers(self):
+        """
+        Verify backwards compatibility by comparing ``storage_index_hash`` outputs
+        for some well-known (to us) inputs.
+        """
+        # This is a marginal case.  b"" is not a valid aes 128 key.  The
+        # implementation does nothing to avoid producing a result for it,
+        # though.
         self._testknown(hashutil.storage_index_hash, b"qb5igbhcc5esa6lwqorsy7e6am", b"")
+
+        # This is a little bit more realistic though clearly this is a poor key choice.
+        self._testknown(hashutil.storage_index_hash, b"wvggbrnrezdpa5yayrgiw5nzja", b"x" * 16)
+
+        # Here's a much more realistic key that I generated by reading some
+        # bytes from /dev/urandom.  I computed the expected hash value twice.
+        # First using hashlib.sha256 and then with sha256sum(1).  The input
+        # string given to the hash function was "43:<storage index tag>,<key>"
+        # in each case.
+        self._testknown(
+            hashutil.storage_index_hash,
+            b"aarbseqqrpsfowduchcjbonscq",
+            base32.a2b(b"2ckv3dfzh6rgjis6ogfqhyxnzy"),
+        )
+
+    def test_known_answers(self):
+        """
+        Verify backwards compatibility by comparing hash outputs for some
+        well-known (to us) inputs.
+        """
         self._testknown(hashutil.block_hash, b"msjr5bh4evuh7fa3zw7uovixfbvlnstr5b65mrerwfnvjxig2jvq", b"")
         self._testknown(hashutil.uri_extension_hash, b"wthsu45q7zewac2mnivoaa4ulh5xvbzdmsbuyztq2a5fzxdrnkka", b"")
         self._testknown(hashutil.plaintext_hash, b"5lz5hwz3qj3af7n6e3arblw7xzutvnd3p3fjsngqjcb7utf3x3da", b"")