Unit test the new storage server backend API.

src/allmydata/storage/server.py

@@ -695,7 +695,6 @@ class StorageServer(service.MultiService):
 
         Raises ``KeyError`` if the storage index is not known.
         """
-        # TODO unit test
         si_dir = storage_index_to_dir(storage_index)
         # shares exist if there is a file for them
         bucketdir = os.path.join(self.sharedir, si_dir)

src/allmydata/test/test_storage.py

@@ -1315,6 +1315,31 @@ class MutableServer(unittest.TestCase):
         self.failUnless(isinstance(readv_data, dict))
         self.failUnlessEqual(len(readv_data), 0)
 
+    def test_list_mutable_shares(self):
+        """
+        ``StorageServer.list_mutable_shares()`` returns a set of share numbers
+        for the given storage index, or raises ``KeyError`` if it does not exist at all.
+        """
+        ss = self.create("test_list_mutable_shares")
+
+        # Initially, nothing exists:
+        with self.assertRaises(KeyError):
+            ss.list_mutable_shares(b"si1")
+
+        self.allocate(ss, b"si1", b"we1", b"le1", [0, 1, 4, 2], 12)
+        shares0_1_2_4 = ss.list_mutable_shares(b"si1")
+
+        # Remove share 2, by setting size to 0:
+        secrets = (self.write_enabler(b"we1"),
+                   self.renew_secret(b"le1"),
+                   self.cancel_secret(b"le1"))
+        ss.slot_testv_and_readv_and_writev(b"si1", secrets, {2: ([], [], 0)}, [])
+        shares0_1_4 = ss.list_mutable_shares(b"si1")
+        self.assertEqual(
+            (shares0_1_2_4, shares0_1_4),
+            ({0, 1, 2, 4}, {0, 1, 4})
+        )
+
     def test_bad_magic(self):
         ss = self.create("test_bad_magic")
         self.allocate(ss, b"si1", b"we1", next(self._lease_secret), set([0]), 10)