tns names could not resolve service name

[elintrend]

step1
ping test2 from test2 and from test1 and oracle816.

I have similar problem before.
find your ip address (test2 ping test2)
find your ip (test1/oracle816 ping test2)

if ip returned not the same, check your network admin,
test2 may have 2 network adaptor...

last time, we disabled one and resovled the problem.

give it a try