Address some review comments

bindings/bindingtester/tests/directory.py

@@ -400,9 +400,10 @@ def generate_path(min_length=0):
 
 
 def generate_prefix(require_unique=False, is_partition=False, min_length=1):
+    fixed_prefix = 'abcdefg'
     if not require_unique and min_length == 0 and random.random() < 0.8:
         return None
-    elif require_unique or is_partition or min_length > len('abcdefg') or random.random() < 0.5:
+    elif require_unique or is_partition or min_length > len(fixed_prefix) or random.random() < 0.5:
         if require_unique:
             min_length = max(min_length, 16)
 
@@ -416,6 +417,6 @@ def generate_prefix(require_unique=False, is_partition=False, min_length=1):
         else:
             return ''.join(chr(random.randrange(ord('\x02'), ord('\x14'))) for i in range(0, length))
     else:
-        prefix = 'abcdefg'
+        prefix = fixed_prefix 
         generated = prefix[0:random.randrange(min_length, len(prefix))]
         return generated

bindings/bindingtester/tests/directory_state_tree.py

@@ -3,13 +3,14 @@ import sys
 class TreeNodeState:
     def __init__(self, dir_id, is_directory, is_subspace, has_known_prefix, root, is_partition):
         self.dir_id = dir_id
-        self.root = root
         self.is_directory = is_directory
         self.is_subspace = is_subspace
         self.has_known_prefix = has_known_prefix
+        self.root = root
+        self.is_partition = is_partition
+
         self.children = {}
         self.deleted = False
-        self.is_partition = is_partition
 
 class Pointer:
     def __init__(self, obj):
@@ -21,13 +22,15 @@ class Pointer:
     def set(self, obj):
         self.obj = obj
 
-# Represents an element of the directory hierarchy, which could have multiple states 
+# Represents an element of the directory hierarchy. As a result of various operations (e.g. moves) that
+# may or may not have succeeded, a node can represent multiple possible states.
 class DirectoryStateTreeNode:
     # A cache of directory layers. We mustn't have multiple entries for the same layer
     layers = {}
 
-    # This is the directory that gets used if the chosen directory is invalid
-    # We must assume any operation could also have been applied to it
+    # Because our operations may be applied to the default directory in the case that
+    # the current directory failed to open/create, we compute the result of each operation
+    # as if it was performed on the current directory and the default directory.
     default_directory = None
 
     # Used for debugging