'L{Data.render} returns an empty response body for a I{HEAD} request.'

def test_headRequest(self):

    data = static.Data('foo', 'bar')
    request = DummyRequest([''])
    request.method = 'HEAD'
    d = _render(data, request)
    def cbRendered(ignored):
        self.assertEqual(''.join(request.written), '')
    d.addCallback(cbRendered)
    return d
