Based on API 589 closure test requirements, some passing (leakage) is permitted during manufacturer shop closure test.
You know that the test pressure during line hydrotest at site may be lower than that during shop closure test.
There is always a limit to what the valve manufacturor will allow as maximum for a valve at a line test. This is partly given by the valve standard, wich will be higher for the housing (open valve housing test 1,5 times pressure class (or more depending on pressure class, dimension and producer and valvetype)) than the seat (operating pressure equal to pressure class normally 1,1 times (again also depending on valve type - for instance will often smaller valves (ball valves for instanca) over-qualify) on allowed seat pressure.
Under line pressure tests there is always a risk of something malfunctioning and giving water hammer, which in addition to overpressure of seats can damage (permanently) the valve sealing or valves.
Generally: blinds should be used and all valves be left open under line tests.
Or (the world is not always ideal) if valves are closed under line-tests, all care should be taken, the valve manufacturor to allow in writing the given pressure.
Two buts: For some types of resilient seated gate-valves for instance, a somewhat higer seat pressure will have less impact than for other constructions.
Secondly: anything going wrong and valves not operating properly or leaking after a (too high) test the responsibillity and guarantee that everything was done properly lies on the test executing side.

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