add get_smallest_folder method and test

tests/test_osd.py

+import unittest
+import random
+
+from xtreemfs_client import osd
+
+
+class TestOsd(unittest.TestCase):
+    def test_get_smallest_folder(self):
+        test_folders = [("folder_1", 1), ("folder_2", 2), ("folder_3", 3), ("folder_4", 4)]
+        for i in range(0, 10):
+            test_osd = osd.OSD("osd_uuid")
+            random.shuffle(test_folders)
+            for folder_id, folder_size in test_folders:
+                test_osd.add_folder(folder_id, folder_size)
+            self.assertEqual(("folder_1", 1), test_osd.get_smallest_folder())

xtreemfs_client/osd.py

@@ -31,6 +31,15 @@ class OSD(object):
     def contains_folder(self, folder_id):
         return folder_id in self.folders
 
+    def get_smallest_folder(self):
+        smallest_id = None
+        smallest_size = 0
+        for id, size in self.folders.items():
+            if smallest_id is None or size < smallest_size:
+                smallest_id, smallest_size = id, size
+
+        return smallest_id, smallest_size
+
     def __str__(self):
         return "osd: '" + self.uuid \
                + "' totalFolderSize: " + str(self.total_folder_size) \