I've found a couple of test reports on other RTGs designed for space. First, from A report on RTGs for Pluto and other missions post 2006:
The RTGs (Qualification Unit and flight units) were assembled in the
Inert Atmosphere Assembly Chamber (IAAC) at Mound (except for F-8
which was assembled at INL). Mound and INL performed initial RTG
Heat transfers in one of three ways: convection, conduction, and/or radiation.
In the vacuum of space, radiation is the primary mechanism of heat leaving a spacecraft. Radiation is slow acting and relatively easy to insulate against.
In a high altitude balloon, objects passing through the cool air outside readily transfer their heat to the surrounding ...
From the Apollo Document NASA TN D-6724
APOLLO EXPERIENCE REPORT -
LUNAR MODULE ENVIRONMENTAL
a large descent-stage gaseous oxygen tank (approximately 48-pound
capacity at 3000 psi) and two ascent-stage gaseous oxygen tanks
(approximately 2.4-pound capacity each at 900 psi).
A pressure regulator was used to reduce the high pressure ...
The LEM had ...
... four oxygen supplies : two, in the descent stage, provide oxygen
during the descent and lunar- stay phases of the mission: two, in the
ascent stage, during the ascent and rendezvous phases of the mission.
The caution and warning limit values can tell us the range of pressures expected to be nominal.
Unsurprisingly, it worked exactly like it did in shuttle.
To assure uniform flow, the capillary restrictors are coiled around a
warm water-glycol line to increase the oxygen temperature.
The aforementioned oxygen supply capillary restrictors are wound
around the line routed to the space radiators and relief valves. The
other line is ...