The ornamental design for a tonetester, as shown and described.
FIG. 1 is a perspective view of an embodiment of a tone tester according to my design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a side view thereof;
FIG. 6 is a side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
Broken lines having repeated short dashes in the Figures are for illustrative purposes only and form no part of the claimed design. Shade lines having a combination of long and short lines in the Figures show contour and not surface ornamentation.