No idea if there is a test programme.
What these things do do is on the heater there are two stats. One with a rest button and the other stat is really a thermistor (but does not look like your normal torpedo styled one. It was pretty common, from memory, that that thermistor stat went to varying degrees to earth which caused the problem you have without taking out the house trip (if you have one). You might want to whip the back plate off the machine (noting the differing screw positions) and test the themistor ideally with a megga. If this is the culprit you cange the heater as one unit. Sure that you cannot buy the thermister by itself! You want to check this first before thinking gambling on a going down the pcboard route.