I am evaluating Oracle SQL Developer.
My tnsnames.ora is populated, and a tnsping to a connection defined in tnsnames.ora work
tnsnames.ora
tnsping
This helped me:
Posted: 8/12/2011 4:54
Set tnsnames directory tools->Preferences->Database->advanced->Tnsnames Directory
https://forums.oracle.com/forums/thread.jspa?messageID=10020012