Use sort for order-independent test

Author: mrkn

test/test-utils.rb

@@ -1,8 +1,8 @@
 class UnicodePlotTest < Test::Unit::TestCase
   test("UnicodePlot.canvas_types") do
     available_canvas_types = [:ascii, :block, :braille, :density, :dot]
-    assert_equal(available_canvas_types,
-                 UnicodePlot.canvas_types)
+    assert_equal(available_canvas_types.sort,
+                 UnicodePlot.canvas_types.sort)
   end
 
   test("UnicodePlot.border_types") do