Whirlpool Dryer Thermal Fuse
 

How can I test the THERMAL FUSE of my Whirlpool dryer is working or not?

With an ohmmeter. When it is cold it should measure as a short.

If you do not own an ohmmeter take your part to the supply house as they may be willing to test her for you.

These things do seem to be one of the usual suspects in dryers not heating up. While you have her apart is a good time to clean out the vent system.

Temporarily install a jumper wire or connect the two leads from each end of the fuse together (effectively bypassing the fuse), if the fuse is bad the dryer will heat up.