diff --git a/spec/filters/mutate.rb b/spec/filters/mutate.rb
new file mode 100644
index 000000000..fb301179e
--- /dev/null
+++ b/spec/filters/mutate.rb
@@ -0,0 +1,59 @@
+require "test_utils"
+require "logstash/filters/mutate"
+
+describe LogStash::Filters::Mutate do
+  extend LogStash::RSpec
+
+  describe "basics" do
+    # The logstash config goes here.
+    # At this time, only filters are supported.
+    config <<-CONFIG
+      filter {
+        mutate {
+          lowercase => "lowerme"
+          uppercase => "upperme"
+          convert => [ "intme", "integer", "floatme", "float" ]
+          rename => [ "rename1", "rename2" ]
+          replace => [ "replaceme", "hello world" ]
+          remove => [ "removeme" ] 
+        }
+      }
+    CONFIG
+
+    event = { "@fields" => { 
+      "lowerme" => [ "ExAmPlE" ], "upperme" => [ "ExAmPlE" ],
+      "intme" => [ "1234" ], "floatme" => [ "1234.455" ],
+      "rename1" => [ "hello world" ],
+      "replaceme" => [ "who cares" ],
+      "removeme" => [ "something" ] 
+      } 
+    } 
+    
+    sample event do
+      insist { subject["lowerme"] } == subject["lowerme"].collect(&:downcase)
+      insist { subject["upperme"] } == subject["lowerme"].collect(&:upcase)
+      insist { subject["intme"] } == subject["intme"].collect(&:to_i)
+      insist { subject["floatme"] } == subject["floatme"].collect(&:to_f)
+      reject { subject }.include?("rename1")
+      insist { subject["rename2"] } == [ "hello world" ]
+      reject { subject }.include?("removeme")
+    end
+  end
+
+  describe "regression - check grok+mutate" do
+    config <<-CONFIG
+      filter {
+        grok {
+          pattern => "%{WORD:foo}"
+        }
+        mutate {
+          lowercase => "foo"
+        }
+      }
+    CONFIG
+
+    sample "HELLO WORLD" do
+      insist { subject["foo"] } == subject["foo"].collect(&:downcase)
+    end
+  end
+end