Was testing some stuff, confirmed three things.
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Test: Electric Terrain's Sleep Prevention
To find out what kind of sleep prevention effect Elec Terrain's sleep immunity effect was, whether it is similar to Leaf Guard in only preventing sleep on use or Insomnia in that it'll outright make it immune to sleep. The test would be to put a Pokemon of my own to sleep using Rest (In this case Doublade) then switching out to a Magneton who'd set a Electric Terrain before switching Doublade back in.
Conclusion:
It is similar to Leaf Guard or Safeguard that it only prevents going to sleep but does not wake up already sleeping Pokemon as the Doublade remained asleep.
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Test: Electric Terrain's Effect on Electric Immunity abilities
Straightforward test to see if it triggers abilities like Lightning Rod or Volt Absorb, simply activated Electric Terrain on Pokemon with these abilities.
Conclusion:
Debunked. Electric Terrain does not have any effect on them.
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Test: The priority order of Electric types immunity to paralysis vs ability
I recall someone asking before whether Thunder Wave failing would take priority or whether electric attack immune abilities take priority. Simple test was to Thunder Wave a bunch of Motor Drive, Lightning Rod and Volt Absorb Pokemon.
Conclusion:
Abilities take priority, where Thunder Wave would simply fail against Electric type Pokemon. If it is used on a Electric type with Volt Absorb, Lightning Rod or Motor Drive then Thunder Wave will hit and activate the abilities therefore abilities have priority over Electric's immunity to paralysis.
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