The ornamental design for the surface testing machine, as shown and described.
FIG. 1 is a front and top-right perspective view of a surface testing
machine showing our new design with the upper portions thereof in a
upwardly tilted position;
FIG. 2 is a front and top-left perspective view thereof;
FIG. 3 is a top and left front perspective view thereof with the paper
receiver cover open and the upper portions in the down position;
FIG. 4 is a top and right rear perspective view of FIGS. 1 and 2.