def METHOD_NAME(runtime, dt):
    # A linear field where advected particles are moving at
    # 1 m/s in the longitudinal direction.
    xdim, ydim = (10, 20)
    Uflow = Field('U', np.ones((ydim, xdim), dtype=np.float64),
                  lon=np.linspace(0., 1e3, xdim, dtype=np.float64),
                  lat=np.linspace(0., 1e3, ydim, dtype=np.float64))
    Vflow = Field('V', np.zeros((ydim, xdim), dtype=np.float64), grid=Uflow.grid)
    fieldset = FieldSet(Uflow, Vflow)
    # Execute the advection kernel only
    pset = ParticleSet(fieldset, pclass=ScipyParticle, lon=[2], lat=[2])
    pset.execute(AdvectionRK4, runtime=runtime, dt=dt)
    # Execute both the advection and interaction kernel.
    pset2 = ParticleSet(fieldset, pclass=ScipyInteractionParticle, lon=[2], lat=[2], interaction_distance=1)
    pyfunc_inter = pset2.InteractionKernel(ConstantMoveInteraction)
    pset2.execute(AdvectionRK4, pyfunc_inter=pyfunc_inter, runtime=runtime, dt=dt)
    # Check to see whether they have moved as predicted.
    assert np.all(pset.lon == pset2.lon)
    assert np.all(pset2.lat == pset2.lon)
    assert np.all(pset2._collection.data["time"][0] == pset._collection.data["time"][0])