diff --git a/test/test_filters.rb b/test/test_filters.rb
index 35ea6f0b..a6be0800 100644
--- a/test/test_filters.rb
+++ b/test/test_filters.rb
@@ -221,6 +221,10 @@ class TestFilters < Test::Unit::TestCase
       should "return a slugified string" do
         assert_equal "q-bert-says", @filter.slugify(" Q*bert says @!#?@!")
       end
+
+      should "return a slugified string with mode" do
+        assert_equal "q-bert-says-@!-@!", @filter.slugify(" Q*bert says @!#?@!", "pretty")
+      end
     end
 
     context "push filter" do
diff --git a/test/test_utils.rb b/test/test_utils.rb
index ddc8750e..fc2d9b5d 100644
--- a/test/test_utils.rb
+++ b/test/test_utils.rb
@@ -139,6 +139,26 @@ class TestUtils < Test::Unit::TestCase
       Utils.slugify(title)
       assert_equal "Quick-start guide", title
     end
+
+    should "not change behaviour if mode is default" do
+      assert_equal "the-config-yml-file", Utils.slugify("The _config.yml file?", "default")
+    end
+
+    should "not change behaviour if mode is nil" do
+      assert_equal "the-config-yml-file", Utils.slugify("The _config.yml file?", nil)
+    end
+
+    should "not replace period and underscore if mode is pretty" do
+      assert_equal "the-_config.yml-file", Utils.slugify("The _config.yml file?", "pretty")
+    end
+
+    should "only replace whitespace if mode is raw" do
+      assert_equal "the-_config.yml-file?", Utils.slugify("The _config.yml file?", "raw")
+    end
+
+    should "return the given string if mode is none" do
+      assert_equal "the _config.yml file?", Utils.slugify("The _config.yml file?", "none")
+    end
   end
 
 end