Prevent duplicates. Refreshing the page successfully gives a different result every time.

app/controllers/movies_controller.rb

@@ -1,8 +1,8 @@
 class MoviesController < ApplicationController
     def index
-        @movies = ["Iron Man", "Batman", "Forrest Gump"]
+        @choices, @movies = ["Iron Man", "Batman", "Forrest Gump"], []
         (0..15).each{ |num|
-            @movies.append(@movies.sample())
+            @movies.append(@choices.sample())
         }
     end
 end