def test_heuristic(): x = Symbol("x", extended_real=True) assert heuristics(sin(1/x) + atan(x), x, 0, '+') == sin(oo) assert heuristics(log(2 + sqrt(atan(x))*sin(1/x)), x, 0, '+') == log(2) assert heuristics(tan(tan(1/x)), x, 0, '+') is None