code: func (c *testCluster) CreateService(name string, instances int) (string, error) {
  	spec := &api.ServiceSpec{
  		Annotations: api.Annotations{Name: name},
  		Mode: &api.ServiceSpec_Replicated{
  			Replicated: &api.ReplicatedService{
  				Replicas: uint64(instances),
  			},
  		},
  		Task: api.TaskSpec{
  			Runtime: &api.TaskSpec_Container{
  				Container: &api.ContainerSpec{Image: "alpine", Command: []string{"sh"}},
  			},
  		},
  	}
  
  	resp, err := c.api.CreateService(context.Background(), &api.CreateServiceRequest{Spec: spec})
  	if err != nil {
  		return "", err
  	}
  	return resp.Service.ID, nil
  }
docs: // CreateService creates dummy service.