Testing graphic LCD without code and wiring
It is not possible to test the module without wiring it to a microcontroller. 
When power is applied to the module, the display remains off and uninitialized.
In order to turn on the display, you need to initialize the display with certain commands and parameters. After which you can send characters to the display. This requires it to be wired to an intelligent chip like a microcontroller that can carry out the commands to initialize the module.

Edit:
There are also other impractical ways to drive these modules as suggested in other posts.