The ornamental design for a specimentestingtray, as shown and described.
FIG. 1 is a top prespective view of a specimen testing tray according to the present invention;
FIG. 2 is a front elevation view of the specimen testing tray;
FIG. 3 is a right side elevation view of the specimen testing tray which, is a mirror image of a left side elevation view;
FIG. 4 is a top view of block of the specimen testing tray; and,
FIG. 5 is a bottom view of the specimen testing tray. The broken lines are included for the purpose of illustrating portions of the specimen tray that form no part of the claimed design.