def METHOD_NAME(ph_si: Phonopy):
    """Test displacements of Si."""
    dataset = deepcopy(ph_si.dataset)
    disp_ref = [[0, 0.0, 0.0070710678118655, 0.0070710678118655]]
    np.testing.assert_allclose(ph_si.displacements, disp_ref, atol=1e-8)
    ph_si.generate_displacements()
    np.testing.assert_allclose(ph_si.displacements, disp_ref, atol=1e-8)
    ph_si.dataset = dataset