Javascript is quite different to RGSS :)
I believe your particular code is creating a function in the main execution context (Something you probably wouldn't normally do with plugins).
But you could run it with the script command:
Scene_Test();The brackets after the function name is how you execute functions in Javascript.I recommend looking at plugins others have created as a good place to see how people do things differently :)
Calling an actual scene in MV is done by using:
SceneManager.push(Scene_Name);But that requires more coding to set the scene up.