actually no my auto darkening HF black helmet (was $30 on sale) is also solar powered but it's got a battery backup and you need to turn it on (press a little digital on button on the op left corner of the mask) to get it to work normally, and the sun test works fine. it defaults at like 70% dark when off, so when you successfully turn it on, the view through the glass gets much brighter, then when you point it fairly rapidly at a bright light (bulb, sun, etc) it flicks to 100% dark. theres also a red LED when you switch it on so you know for sure.
the "solar" charging (charging when welding using the welding spark's light) is technically not needed to operate, it does work on battery only, but you'll run out of battery at some point if you tape up or cover the solar panel above the glass. if you keep the solar cell clean so it's got full light to charge the battery, the mask will never need to be charged [in the sun or w/e] when not in use.
hope that helps.
edit: also if the light source you're testing on isn't quite bright enough, like a neon type light, the mask may flicker bright/dark but thats just cuz its on the border of bright enough. the sun should be a decent testing light.