Re: Uh ho ...
This one's old enough that it's hardware rather than software testing.
Vinten Communications used to make the radio equipment used by the Victorian Police and other emergency services.
This was back in the days of valves and dangerously high voltages.
They had one wiresman in particular who was absolutely meticulous in his work. Every wire of a particular colour entering one end of the loom would exit at precisely the same position with respect to all of its neighbors. This greatly simplified fault finding. (Debugging wasn't yet a part of the common vernacular.) As such, he was the go to person for all new prototypes.
On day however, a new product was put on the test bench for it's first power on. Unbeknown to the wiresman, his colleagues had got there first.
The prototype was duly turned on, and they watched the blood drain from the poor wiresman's face, as smoke started wafting out of the case.
One worker was hidden away out of sight, and a string of waxed paper drinking straws had been run to an inconspicuous location on the unit under test.
The hidden worker was blowing cigarette smoke through the straws.
However one of the observers broke up laughing, and the ruse was revealed, much to the relief and annoyance of the poor wiresman. The device itself worked flawlessly.