'L{static.File.render} returns an empty response body for I{HEAD}
requests.'

def test_headRequest(self):

    path = FilePath(self.mktemp())
    path.setContent('foo')
    file = static.File(path.path)
    request = DummyRequest([''])
    request.method = 'HEAD'
    d = _render(file, request)
    def cbRendered(ignored):
        self.assertEqual(''.join(request.written), '')
    d.addCallback(cbRendered)
    return d
