'If the process ends with a success, the returned deferred fires with
a succesful result.'

def test_process_success(self):

    reactor = ProcessCoreReactor()
    d = run(reactor, ['command', 'and', 'args'])
    [process] = reactor.processes
    expected_failure = Failure(ProcessDone(0))
    process.processProtocol.processEnded(expected_failure)
    self.successResultOf(d)
