Is there any way to use Mathematica to test whether a function is continuous over a given domain? Answer This is likely to be very slow.. isDiscontinuous[f_, low_, high_] := Resolve[Exists[del, del > 0, ForAll[eps, eps > 0, Exists[{x1, x2}, low <= x1 < x2 <= high && x2 - x1 < eps && Abs[f[x1] - f[x2]] > del]]]] Here are simple examples. ff[x_] := x^2 + x isDiscontinuous[ff, -1, 2] (* Out[334]= False *) gg[x_] := Sign[x] Resolve[isDiscontinuous[gg, -1, 2]] (* Out[331]= True *)