Testing a dishwashers components is done with a volt meter, having a volt meter to help with diagnostics is essential.
The heating circuit on a dishwasher contains several parts any of them could cause the dishwasher not to heat possibilities:
-Faulty heater element
-loose or broken wire
-Failed electronic control
Any of these components if broken will create a no heat condition. There is a schematic and wiring diagram on the machine, if you can read a schematic you will see the circuits in the series. If not on some technical schematics there is information on accessing the dishwasher diagnostics.
In diagnostic mode you can manually advance the unit activating all of the functions this will allow voltage tests if needed. This test lets you advance the unit through all available option without having to wait two hours for the cycle to complete.