your mistake is assuming that you have an instance of viewimage when you run:
var vueimage = new (require('UI/viewimage'))();
you are getting an instance of
var lavue = Ti.UI.createView({backgroundColor:'red' });
which doesn't have a test property.
Perhaps you could use an object like this instead:
function viewimage() {
var result = {};
var lavue = Ti.UI.createView({backgroundColor:'red' });
var item =...
lavue.add(item...);
result.lavue = lavue;
result.test = function() {
Ti.API.info("test");
};
return result;
}
EDIT
In your App.js:
var vueimage = new (require('UI/viewimage'))();
vueimage.test();
fenetreBase.add(vueimage.lavue);