def METHOD_NAME(f):
    if f.function_space().mesh().num_cells() == 1:
        # Quadrilateral case, no internal facet
        assert abs(assemble(f('+') * dS)) < 1.0e-14
    else:
        # Triangle case, one internal facet
        assert abs(assemble(f('+') * dS) - 1.0 / (2.0 ** 0.5)) < 1.0e-14