def test_separate_by_order(): u, v = Variables('u v') c, f = Constants('c f') strong_form = StrongForm(c*grad(div(u)) + div(v) - f + dot(c, grad(u))) order_dict = strong_form.separate_by_order() assert(order_dict[0] == -f) assert(order_dict[1] == div(v) + dot(c, grad(u))) assert(order_dict[2] == c*grad(div(u)))