What is not true for equipotential surface for uniform electric...

An equipotential surface is a surface with a constant value of potential at all points on the surface. For a uniform electric field, say, along the $x$-axis, the equipotential surfaces are planes normal to the $x$-axis, $i e$, plane parallel to the $y$-z plane. Equipotential surfaces for a dipole and its electric field lines are shown in figure. As said above that on equipotential surface, potential at all points is constant, this means that on equipotential surface work done in moving a test charge from one point to other point is zero.