If you judge damage may occur you do not have to test. Testing TP has a high rate of valve leaks afterwards. If you do not test it you are required to say “not inspected” and specify a reason why per Departure Rules.
(A) An inspector may depart from the inspection of a component or system required by the standards of practice only if:
(v) the inspector reasonably determines that conditions or materials are hazardous to the health or safety of the inspector;
(vi) in the reasonable judgment of the inspector, the actions of the inspector may cause damage to the property.
(B) If an inspector departs from the inspection of a component or system required by the standards of practice, the inspector shall:
(i) notify the client at the earliest practical opportunity that the component or system will not be inspected; and
(ii) make an appropriate notation on the inspection report form, stating the reason the component or system was not inspected.
© If the inspector routinely departs from inspection of a component or system required by the standards of practice, and the inspector has reason to believe that the property being inspected includes that component or system, the earliest practical opportunity for the notice required by this subsection is the first contact the inspector makes with the prospective client.
Some argue the earliest moment to notify the client is immediately, however I just do it in report. “The water heater TP valve was not tested to avoid causing a leak.”
The departure rule is the most important item to comply with.
I very rarely test one. I suspect 50% will leak. I have never had a complaint on it.