What is the toughest part about Electrical testing?

The toughest part of electrical testing is when everything are installed and connected then the system doesn't meet the condition of the working operation.
That is where your expertise will emerged adjusting to the condition that will meet the requirements sometimes beyond the limit of performance but with in safe aspect.
Electrical testing sometimes will put your analytical techniques to answer why it doesn't work when you follow everything base on the plan.

The toughest part of electrical testing is the ((Time)) ...
when you trying hard to challnge the time to find the problem >> the professional testing engineer who find the problem as fast as possible without affecting the system continuity