Argument ‘fn’ is not a function got string

The problem was in using the ‘wrong’ syntax to create the service
instead of using:

messageServices.factory('MessageService', 
    ['MessageData','localStorageService', 'UserService'], 
    function(MessageData, localStorageService, UserService){
        return new MessageService(MessageData, localStorageService, UserService);
    }
);

I had to use:

messageServices.factory('MessageService', 
    ['MessageData','localStorageService', 'UserService', 
    function(MessageData, localStorageService, UserService){
        return new MessageService(MessageData, localStorageService, UserService);
    }
]);

I closed the array with parameters to soon, and since I’m still learning I didn’t see it directly, anyhow I hope I can help others who stumble upon this.