tests: helpers: use less random data

We do not need really random data in the files we generate - this only slows
the tests down a lot. Let's fill the files with semi-random data instead - just
pick a random byte and fill large regions with this byt. This also make
compression work faster, and it is good enough for our purposes.

Besides, this allows to reproduce tests by setting a known seed, which does not
work with os.urandom.

Change-Id: I0459ee44d271b8e19581e84cc33b7167e4ada166
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@intel.com>

diff --git a/tests/helpers.py b/tests/helpers.py
index 99015bb..45e03c3 100644 (file)
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -5,7 +5,6 @@ tests. """
 #   * Too many statements (R0915)
 # pylint: disable=R0915
 
-import os
 import tempfile
 import random
 import itertools
@@ -13,7 +12,7 @@ from bmaptools import BmapHelpers
 
 def create_random_sparse_file(file_obj, size):
     """ Create a sparse file with randomly distributed holes. The mapped areas
-    are filled with random data. Returns a tuple containing 2 lists:
+    are filled with semi-random data. Returns a tuple containing 2 lists:
       1. a list of mapped block ranges, same as 'Fiemap.get_mapped_ranges()'
       2. a list of unmapped block ranges (holes), same as
          'Fiemap.get_unmapped_ranges()' """
@@ -32,7 +31,7 @@ def create_random_sparse_file(file_obj, size):
 
         if map_the_block:
             file_obj.seek(block * block_size)
-            file_obj.write(bytearray(os.urandom(block_size)))
+            file_obj.write(chr(random.getrandbits(8)) * block_size)
         else:
             file_obj.truncate((block + 1) * block_size)
 
@@ -60,7 +59,7 @@ def create_random_sparse_file(file_obj, size):
     return (mapped, holes)
 
 def _create_random_file(file_obj, size):
-    """ Fill the 'file_obj' file object with random data up to the size
+    """ Fill the 'file_obj' file object with semi-random data up to the size
     'size'. """
 
     chunk_size = 1024 * 1024
@@ -70,7 +69,7 @@ def _create_random_file(file_obj, size):
         if written + chunk_size > size:
             chunk_size = size - written
 
-        file_obj.write(bytearray(os.urandom(chunk_size)))
+        file_obj.write(chr(random.getrandbits(8)) * chunk_size)
         written += chunk_size
 
     file_obj.flush()