From: Zooko O'Whielacronx <zooko@zooko.com>
Date: Thu, 31 Jul 2008 00:20:15 +0000 (-0700)
Subject: tests: add test that verifier notices any (randomly chosen) bit flipped in the verifi... 
X-Git-Url: https://git.rkrishnan.org/architecture.txt?a=commitdiff_plain;h=6d3ec390b04a8fd54b363813b80ca91b94b3f966;p=tahoe-lafs%2Ftahoe-lafs.git

tests: add test that verifier notices any (randomly chosen) bit flipped in the verifiable part of any (randomly chosen) share
The currently verifier doesn't (usually) pass this randomized test, hence the TODO.
---

diff --git a/src/allmydata/test/test_system.py b/src/allmydata/test/test_system.py
index 70620333..d26c8b16 100644
--- a/src/allmydata/test/test_system.py
+++ b/src/allmydata/test/test_system.py
@@ -1,5 +1,5 @@
 from base64 import b32encode
-import os, random, sys, time, re, simplejson
+import os, random, struct, sys, time, re, simplejson
 from cStringIO import StringIO
 from twisted.trial import unittest
 from twisted.internet import defer
@@ -1712,7 +1712,7 @@ class Checker(SystemTestMixin, unittest.TestCase):
         # Set self.basedir to a temp dir which has the name of the current test method in its
         # name.
         self.basedir = self.mktemp()
-        TEST_DATA="\x02"*1000
+        TEST_DATA="\x02"*(upload.Uploader.URI_LIT_SIZE_THRESHOLD+1)
 
         d = defer.maybeDeferred(SystemTestMixin.setUp, self)
         d.addCallback(lambda x: self.set_up_nodes())
@@ -1764,12 +1764,21 @@ class Checker(SystemTestMixin, unittest.TestCase):
                             open(pathtosharefile, "w").write(newdata)
 
     def _corrupt_a_share(self, unused=None):
-        """ Exactly one bit of exactly one share on disk will be flipped (randomly selected). """
+        """ Exactly one bit of exactly one share on disk will be flipped (randomly selected from
+        among the bits of the 'share data' -- the verifiable bits)."""
+
         shares = self._find_shares()
         ks = shares.keys()
         k = random.choice(ks)
         data = shares[k]
-        shares[k]  = testutil.flip_one_bit(shares[k])
+
+        (version, size, num_leases) = struct.unpack(">LLL", data[:0xc])
+        sharedata = data[0xc:0xc+size]
+
+        corruptedsharedata = testutil.flip_one_bit(sharedata)
+        corrupteddata = data[:0xc]+corruptedsharedata+data[0xc+size:]
+        shares[k] = corrupteddata
+
         self._replace_shares(shares)
 
     def test_test_code(self):
@@ -1855,3 +1864,39 @@ class Checker(SystemTestMixin, unittest.TestCase):
         d.addCallback(_check3)
 
         return d
+
+    def test_check_with_verify(self):
+        """ Check says the file is healthy when none of the shares have been touched.  It says
+        that the file is unhealthy if one bit of one share has been flipped."""
+        DELTA_READS = 10 * 2 # N == 10
+        d = defer.succeed(self.filenode)
+        def _check1(filenode):
+            before_check_reads = self._count_reads()
+
+            d2 = filenode.check(verify=True, repair=False)
+            def _after_check(checkresults):
+                after_check_reads = self._count_reads()
+                # print "delta was ", after_check_reads - before_check_reads
+                self.failIf(after_check_reads - before_check_reads > DELTA_READS)
+                self.failUnless(checkresults.is_healthy())
+
+            d2.addCallback(_after_check)
+            return d2
+        d.addCallback(_check1)
+
+        d.addCallback(self._corrupt_a_share)
+        def _check2(ignored):
+            before_check_reads = self._count_reads()
+            d2 = self.filenode.check(verify=True, repair=False)
+
+            def _after_check(checkresults):
+                after_check_reads = self._count_reads()
+                # print "delta was ", after_check_reads - before_check_reads
+                self.failIf(after_check_reads - before_check_reads > DELTA_READS)
+                self.failIf(checkresults.is_healthy())
+
+            d2.addCallback(_after_check)
+            return d2
+        d.addCallback(_check2)
+        return d
+    test_check_with_verify.todo = "We haven't implemented a verifier this thorough yet."