Add test to ensure plugins are executed in order of priority.

test/source/_plugins/dummy.rb

@@ -0,0 +1,8 @@
+module Jekyll
+  class Dummy < Generator
+    priority :high
+
+    def generate(site)
+    end
+  end
+end

test/test_site.rb

@@ -124,6 +124,11 @@ class TestSite < Test::Unit::TestCase
       assert_equal mtime3, mtime4 # no modifications, so must be the same
     end
 
+    should "setup plugins in priority order" do
+      assert_equal @site.converters.sort_by(&:class).map{|c|c.class.priority}, @site.converters.map{|c|c.class.priority}
+      assert_equal @site.generators.sort_by(&:class).map{|g|g.class.priority}, @site.generators.map{|g|g.class.priority}
+    end
+
     should "read layouts" do
       @site.read_layouts
       assert_equal ["default", "simple"].sort, @site.layouts.keys.sort