refining and getting tests for placeholder

lib/squib/args/arg_loader.rb

@@ -126,4 +126,13 @@ module Squib::Args::ArgLoader
     self
   end
 
+  # Return the deck's configuration
+  # This keeps the @deck local to this mixin instead of forcing args classes
+  # to "know" that @deck works.
+  #
+  # It also makes unit testing easier. Sue me.
+  def deck_conf
+    @deck.conf
+  end
+
 end

lib/squib/args/input_file.rb

@@ -30,9 +30,9 @@ module Squib::Args
     def validate_file(arg, i)
       return nil if arg.nil?
       return File.expand_path(arg) if File.exists?(arg)
-      return File.expand_path(placeholder[i]) if File.exists?(placeholder[i])
+      return File.expand_path(placeholder[i]) if File.exists?(placeholder[i].to_s)
 
-      case @deck.conf.img_missing.to_sym
+      case deck_conf.img_missing.to_sym
       when :error
         raise "File #{File.expand_path(arg)} does not exist!"
       when :warn