def test_cartesian_cell_volume():
    basis = np.array([
        [1., 0., 0.],
        [0., 1., 0.],
        [0., 0., 1.]
        ]).astype('d')
    reference_volume = 1.
    volume = get_elementary_cell_volume(basis)
    assert abs(reference_volume - volume) < 1e-6
    return
def test_reciprocal_ZnS_volume():
    basis = 0.5 * np.array([
        [0., 1., 1.],
        [1., 0., 1.],
        [1., 1., 0.]
        ]).astype('d')
    reciprocal_basis = get_reciprocal_space_elementary_vectors(basis)
    reference_volume = 4 * (2*pi) ** 3
    volume = get_elementary_cell_volume(reciprocal_basis)
    assert abs(reference_volume - volume) < 1e-6
    return