def Grow(self, amount, dryrun, backingstore, _excl_stor):
    # Check that the file exists
    self.Exists(assert_exists=True)

    if amount < 0:
      base.ThrowError("%s: can't grow by negative amount", self.path)

    if dryrun:
      return
    if not backingstore:
      return

    current_size = self.Size()
    new_size = current_size + amount * 1024 * 1024
    try:
      f = open(self.path, "a+")
      f.truncate(new_size)
      f.close()
    except EnvironmentError, err:
      base.ThrowError("%s: can't grow: ", self.path, str(err))
Sets up the fixture, and sets self.fixture if needed
dataset/ETHPy150Open ganeti/ganeti/lib/storage/filestorage.py/FileDeviceHelper.Grow--crossover with--dataset/ETHPy150Open edgewall/trac/trac/test.py/TestSetup.setUp