'File updates should only start one MultiGetFile at any point in time.'

def testVFSFileStartsOnlyOneMultiGetFileFlowOnUpdate(self):

    client_id = self.SetupClients(1)[0]
    fixture_test_lib.ClientFixture(client_id, token=self.token)
    path = 'fs/os/c/bin/bash'
    with aff4.FACTORY.Create(client_id.Add(path), aff4_type=aff4_grr.VFSFile, mode='rw', token=self.token) as file_fd:
        file_fd.Update()
    flows_fd = aff4.FACTORY.Open(client_id.Add('flows'), token=self.token)
    flows = list(flows_fd.ListChildren())
    self.assertEqual(len(flows), 1)
    flow_obj = aff4.FACTORY.Open(flows[0], token=self.token)
    self.assertEqual(flow_obj.Get(flow_obj.Schema.TYPE), transfer.MultiGetFile.__name__)
    self.assertEqual(flow_obj.urn, file_fd.Get(file_fd.Schema.CONTENT_LOCK))
    file_fd.Update()
    flows_fd = aff4.FACTORY.Open(client_id.Add('flows'), token=self.token)
    flows = list(flows_fd.ListChildren())
    self.assertEqual(len(flows), 1)
