Use stubs in libvirt/utils get_fs_info test

This test frequently breaks for me because of a race condition where
some small change will happen to the file system between when df is
called and when os.statvfs is called. By refactoring the test to stubs,
we can eliminate the race condition. Note that I do not modify the code
under test at all in this change, so the risk of introducing a defect is
zero.

Change-Id: I83e4b38b25fef7e5e27fcf81b5e5a566406b05dd

1 files changed, 28 insertions, 11 deletions

diff --git a/nova/tests/test_libvirt.py b/nova/tests/test_libvirt.py
index 2d50344d6..1f9dc3eb8 100644
--- a/nova/tests/test_libvirt.py
+++ b/nova/tests/test_libvirt.py
@@ -1920,17 +1920,34 @@ disk size: 4.4M''', ''))
             os.unlink(dst_path)
 
     def test_get_fs_info(self):
-        # Use a 1024-byte block size (df -k) because OS X does not support
-        # the -B flag
-        blocksize = 1024
-        stdout, stderr = utils.execute('df', '-k', '/tmp')
-        info_line = ' '.join(stdout.split('\n')[1:])
-        _dev, total, used, free, _percentage, _mntpnt = info_line.split()
-
-        fs_info = libvirt_utils.get_fs_info('/tmp')
-        self.assertEquals(int(total) * blocksize, fs_info['total'])
-        self.assertEquals(int(free) * blocksize, fs_info['free'])
-        self.assertEquals(int(used) * blocksize, fs_info['used'])
+
+        class FakeStatResult(object):
+
+            def __init__(self):
+                self.f_bsize = 4096
+                self.f_frsize = 4096
+                self.f_blocks = 2000
+                self.f_bfree = 1000
+                self.f_bavail = 900
+                self.f_files = 2000
+                self.f_ffree = 1000
+                self.f_favail = 900
+                self.f_flag = 4096
+                self.f_namemax = 255
+
+        self.path = None
+
+        def fake_statvfs(path):
+            self.path = path
+            return FakeStatResult()
+
+        self.stubs.Set(os, 'statvfs', fake_statvfs)
+
+        fs_info = libvirt_utils.get_fs_info('/some/file/path')
+        self.assertEquals('/some/file/path', self.path)
+        self.assertEquals(8192000, fs_info['total'])
+        self.assertEquals(3686400, fs_info['free'])
+        self.assertEquals(4096000, fs_info['used'])
 
     def test_fetch_image(self):
         self.mox.StubOutWithMock(images, 'fetch')