diff --git a/kong-0.5.4-1.rockspec b/kong-0.5.4-1.rockspec
index 1a60a78d3bd7..bb7853f2c286 100644
--- a/kong-0.5.4-1.rockspec
+++ b/kong-0.5.4-1.rockspec
@@ -167,8 +167,8 @@ build = {
     ["kong.plugins.request-transformer.schema"] = "kong/plugins/request-transformer/schema.lua",
 
     ["kong.plugins.response-transformer.handler"] = "kong/plugins/response-transformer/handler.lua",
-    ["kong.plugins.response-transformer.body_filter"] = "kong/plugins/response-transformer/body_filter.lua",
-    ["kong.plugins.response-transformer.header_filter"] = "kong/plugins/response-transformer/header_filter.lua",
+    ["kong.plugins.response-transformer.body_transformer"] = "kong/plugins/response-transformer/body_transformer.lua",
+    ["kong.plugins.response-transformer.header_transformer"] = "kong/plugins/response-transformer/header_transformer.lua",
     ["kong.plugins.response-transformer.schema"] = "kong/plugins/response-transformer/schema.lua",
 
     ["kong.plugins.cors.handler"] = "kong/plugins/cors/handler.lua",
diff --git a/kong/plugins/response-transformer/body_filter.lua b/kong/plugins/response-transformer/body_filter.lua
deleted file mode 100644
index 8825a0775e7e..000000000000
--- a/kong/plugins/response-transformer/body_filter.lua
+++ /dev/null
@@ -1,92 +0,0 @@
-local utils = require "kong.tools.utils"
-local stringy = require "stringy"
-local cjson = require "cjson"
-
-local _M = {}
-
-local APPLICATION_JSON = "application/json"
-local CONTENT_TYPE = "content-type"
-
-local function get_content_type()
-  local header_value = ngx.header[CONTENT_TYPE]
-  if header_value then
-    return stringy.strip(header_value):lower()
-  end
-  return nil
-end
-
-local function read_response_body()
-  local chunk, eof = ngx.arg[1], ngx.arg[2] 
-  local buffered = ngx.ctx.buffered 
-  if not buffered then 
-    buffered = {}
-    ngx.ctx.buffered = buffered 
-  end
-  if chunk ~= "" then 
-    buffered[#buffered + 1] = chunk 
-    ngx.arg[1] = nil 
-  end
-  if eof then 
-    local response_body = table.concat(buffered) 
-    return response_body
-  end
-  return nil
-end
-
-local function read_json_body()
-  local body = read_response_body()
-  if body then
-    local status, res = pcall(cjson.decode, body)
-    if status then
-      return res
-    end
-  end
-  return nil
-end
-
-local function set_json_body(json)
-  local body = cjson.encode(json)
-  ngx.arg[1] = body
-end
-
-local function iterate_and_exec(val, cb)
-  if utils.table_size(val) > 0 then
-    for _, entry in ipairs(val) do
-      local parts = stringy.split(entry, ":")
-      cb(parts[1], utils.table_size(parts) == 2 and parts[2] or nil)
-    end
-  end
-end
-
-function _M.execute(conf)
-  if not conf then return end
-
-  local is_json_body = stringy.startswith(get_content_type(), APPLICATION_JSON)
-
-  if ((conf.add and conf.add.json) or (conf.remove and conf.remove.json)) and is_json_body then
-    local json_body = read_json_body()
-    if json_body then
-
-      if conf.add and conf.add.json then
-        iterate_and_exec(conf.add.json, function(name, value)
-          local v = cjson.encode(value)
-          if stringy.startswith(v, "\"") and stringy.endswith(v, "\"") then
-            v = v:sub(2, v:len() - 1):gsub("\\\"", "\"") -- To prevent having double encoded quotes
-          end
-          json_body[name] = v
-        end)
-      end
-
-      if conf.remove and conf.remove.json then
-        iterate_and_exec(conf.remove.json, function(name)
-          json_body[name] = nil
-        end)
-      end
-
-      set_json_body(json_body) 
-    end
-  end
-
-end
-
-return _M
diff --git a/kong/plugins/response-transformer/body_transformer.lua b/kong/plugins/response-transformer/body_transformer.lua
new file mode 100644
index 000000000000..0f7a1ab680f6
--- /dev/null
+++ b/kong/plugins/response-transformer/body_transformer.lua
@@ -0,0 +1,93 @@
+local stringy = require "stringy"
+local cjson = require "cjson"
+
+local table_insert = table.insert
+local pcall = pcall
+local string_find = string.find
+local unpack = unpack
+local type = type
+
+local _M = {}
+
+local function read_json_body(body)
+  if body then
+    local status, res = pcall(cjson.decode, body)
+    if status then
+      return res
+    end
+  end
+end
+
+local function append_value(current_value, value)
+  local current_value_type = type(current_value)
+ 
+  if current_value_type  == "string" then
+    return {current_value, value}
+  elseif current_value_type  == "table" then
+    table_insert(current_value, value)
+    return current_value  
+  else
+    return {value} 
+  end
+end
+
+local function iter(config_array)
+  return function(config_array, i, previous_name, previous_value)
+    i = i + 1
+    local current_pair = config_array[i]
+    if current_pair == nil then -- n + 1
+      return nil
+    end
+    local current_name, current_value = unpack(stringy.split(current_pair, ":"))
+    return i, current_name, current_value  
+  end, config_array, 0
+end
+
+function _M.is_json_body(content_type)
+  return content_type and string_find(content_type:lower(), "application/json", nil, true)
+end
+
+function _M.transform_json_body(conf, buffered_data)
+  local json_body = read_json_body(buffered_data)
+  if json_body == nil then return end
+  
+  -- remove key:value to body
+  for _, name in iter(conf.remove.json) do
+    json_body[name] = nil
+  end
+  
+  -- replace  key:value to body
+  for _, name, value in iter(conf.replace.json) do
+    local v = cjson.encode(value)
+    if stringy.startswith(v, "\"") and stringy.endswith(v, "\"") then
+      v = v:sub(2, v:len() - 1):gsub("\\\"", "\"") -- To prevent having double encoded quotes
+    end
+    if json_body[name] then
+      json_body[name] = v
+    end
+  end
+  
+  -- add new key:value to body    
+  for _, name, value in iter(conf.add.json) do
+    local v = cjson.encode(value)
+    if stringy.startswith(v, "\"") and stringy.endswith(v, "\"") then
+      v = v:sub(2, v:len() - 1):gsub("\\\"", "\"") -- To prevent having double encoded quotes
+    end
+    if not json_body[name] then
+      json_body[name] = v
+    end
+  end
+  
+  -- append new key:value or value to existing key    
+  for _, name, value in iter(conf.append.json) do
+    local v = cjson.encode(value)
+    if stringy.startswith(v, "\"") and stringy.endswith(v, "\"") then
+      v = v:sub(2, v:len() - 1):gsub("\\\"", "\"") -- To prevent having double encoded quotes
+    end
+    json_body[name] = append_value(json_body[name],v)
+  end
+  
+  return cjson.encode(json_body) 
+end
+
+return _M
diff --git a/kong/plugins/response-transformer/handler.lua b/kong/plugins/response-transformer/handler.lua
index b4d442465f6d..f6f176ef0743 100644
--- a/kong/plugins/response-transformer/handler.lua
+++ b/kong/plugins/response-transformer/handler.lua
@@ -1,6 +1,6 @@
 local BasePlugin = require "kong.plugins.base_plugin"
-local body_filter = require "kong.plugins.response-transformer.body_filter"
-local header_filter = require "kong.plugins.response-transformer.header_filter"
+local body_filter = require "kong.plugins.response-transformer.body_transformer"
+local header_filter = require "kong.plugins.response-transformer.header_transformer"
 
 local ResponseTransformerHandler = BasePlugin:extend()
 
@@ -8,14 +8,28 @@ function ResponseTransformerHandler:new()
   ResponseTransformerHandler.super.new(self, "response-transformer")
 end
 
+function ResponseTransformerHandler:access(conf)
+  ResponseTransformerHandler.super.access(self)
+  ngx.ctx.buffer = ""
+end
+
 function ResponseTransformerHandler:header_filter(conf)
   ResponseTransformerHandler.super.header_filter(self)
-  header_filter.execute(conf)
+  header_filter.transform_headers(conf, ngx.header)
 end
 
 function ResponseTransformerHandler:body_filter(conf)
   ResponseTransformerHandler.super.body_filter(self)
-  body_filter.execute(conf)
+  if body_filter.is_json_body(ngx.header["content-type"]) then
+    local chunk, eof = ngx.arg[1], ngx.arg[2]
+    if eof then
+      local body = body_filter.transform_json_body(conf, ngx.ctx.buffer)
+      ngx.arg[1] = body
+    else
+      ngx.ctx.buffer = ngx.ctx.buffer..chunk
+      ngx.arg[1] = nil
+    end  
+  end  
 end
 
 ResponseTransformerHandler.PRIORITY = 800
diff --git a/kong/plugins/response-transformer/header_filter.lua b/kong/plugins/response-transformer/header_filter.lua
deleted file mode 100644
index 217b9c4b32aa..000000000000
--- a/kong/plugins/response-transformer/header_filter.lua
+++ /dev/null
@@ -1,64 +0,0 @@
-local utils = require "kong.tools.utils"
-local stringy = require "stringy"
-
-local _M = {}
-
-local APPLICATION_JSON = "application/json"
-local CONTENT_TYPE = "content-type"
-local CONTENT_LENGTH = "content-length"
-
-local function get_content_type()
-  local header_value = ngx.header[CONTENT_TYPE]
-  if header_value then
-    return stringy.strip(header_value):lower()
-  end
-  return nil
-end
-
-local function iterate_and_exec(val, cb)
-  if utils.table_size(val) > 0 then
-    for _, entry in ipairs(val) do
-      local parts = stringy.split(entry, ":")
-      cb(parts[1], utils.table_size(parts) == 2 and parts[2] or nil)
-    end
-  end
-end
-
-function _M.execute(conf)
-  local is_json_body = stringy.startswith(get_content_type(), APPLICATION_JSON)
-
-  if conf.add then
-
-    -- Add headers
-    if conf.add.headers then
-      iterate_and_exec(conf.add.headers, function(name, value)
-        ngx.header[name] = value
-      end)
-    end
-
-    -- Removing the header because the body is going to change
-    if conf.add.json and is_json_body then
-      ngx.header[CONTENT_LENGTH] = nil
-    end
-
-  end
-
-  if conf.remove then
-
-    -- Remove headers
-    if conf.remove.headers then
-      iterate_and_exec(conf.remove.headers, function(name, value)
-        ngx.header[name] = nil
-      end)
-    end
-
-    -- Removing the header because the body is going to change
-    if conf.remove.json and is_json_body then
-      ngx.header[CONTENT_LENGTH] = nil
-    end
-
-  end
-
-end
-
-return _M
diff --git a/kong/plugins/response-transformer/header_transformer.lua b/kong/plugins/response-transformer/header_transformer.lua
new file mode 100644
index 000000000000..c47105642da0
--- /dev/null
+++ b/kong/plugins/response-transformer/header_transformer.lua
@@ -0,0 +1,77 @@
+local stringy = require "stringy"
+
+local table_insert = table.insert
+local unpack = unpack
+local type = type
+local string_find = string.find
+
+local _M = {}
+
+local function iter(config_array)
+  return function(config_array, i, previous_header_name, previous_header_value)
+    i = i + 1
+    local header_to_test = config_array[i]
+    if header_to_test == nil then -- n + 1
+      return nil
+    end
+    local header_to_test_name, header_to_test_value = unpack(stringy.split(header_to_test, ":"))
+    return i, header_to_test_name, header_to_test_value  
+  end, config_array, 0
+end
+
+local function append_value(current_value, value)
+  local current_value_type = type(current_value)
+
+  if current_value_type == "string" then
+    return {current_value, value}
+  elseif current_value_type == "table" then
+    table_insert(current_value, value)
+    return current_value  
+  else
+    return {value} 
+  end
+end
+
+local function is_json_body(content_type)
+  return content_type and string_find(content_type:lower(), "application/json", nil, true)
+end
+
+---
+--   # Example:
+--   ngx.headers = header_filter.transform_headers(conf, ngx.headers)
+-- We run transformations in following order: remove, replace, add, append. 
+-- @param[type=table] conf Plugin configuration.
+-- @param[type=table] ngx_headers Table of headers, that should be `ngx.headers`
+-- @return table A table containing the new headers.
+function _M.transform_headers(conf, ngx_headers)
+  -- remove headers
+  for _, header_name, header_value in iter(conf.remove.headers) do
+      ngx_headers[header_name] = nil
+  end
+  
+  -- replace headers
+  for _, header_name, header_value in iter(conf.replace.headers) do
+    if ngx_headers[header_name] ~= nil then
+      ngx_headers[header_name] = header_value
+    end
+  end
+  
+  -- add headers
+  for _, header_name, header_value in iter(conf.add.headers) do
+    if ngx_headers[header_name] == nil then
+      ngx_headers[header_name] = header_value
+    end
+  end
+  
+  -- append headers
+  for _, header_name, header_value in iter(conf.append.headers) do
+    ngx_headers[header_name] = append_value(ngx_headers[header_name], header_value)
+  end
+  
+  -- Removing the content-length header because the body is going to change
+  if conf.add.json and is_json_body(ngx_headers["content-type"]) then
+    ngx_headers["content-length"] = nil
+  end
+end
+
+return _M
diff --git a/kong/plugins/response-transformer/schema.lua b/kong/plugins/response-transformer/schema.lua
index db024d57f48f..e2d9522b719d 100644
--- a/kong/plugins/response-transformer/schema.lua
+++ b/kong/plugins/response-transformer/schema.lua
@@ -1,16 +1,39 @@
 return {
   fields = {
-    add = { type = "table", schema = {
+    -- add: Add a value (to response headers or response JSON body) only if the key does not already exist.
+    remove = { 
+      type = "table",
+      schema = {
         fields = {
-          json = { type = "array" },
-          headers = { type = "array" }
+          json = {type = "array", default = {}},
+          headers = {type = "array", default = {}}
         }
       }
     },
-    remove = { type = "table", schema = {
+    replace = {
+      type = "table",
+      schema = {
         fields = {
-          json = { type = "array" },
-          headers = { type = "array" }
+          json = {type = "array", default = {}},
+          headers = {type = "array", default = {}}
+        }
+      }
+    },
+    add = {
+      type = "table",
+      schema = {
+        fields = {
+          json = {type = "array", default = {}},
+          headers = {type = "array", default = {}}
+        }
+      }
+    },
+    append = { 
+      type = "table", 
+      schema = {
+        fields = {
+          json = {type = "array", default = {}},
+          headers = {type = "array", default = {}}
         }
       }
     }
diff --git a/spec/plugins/response-transformer/big_resonse_body_spec.lua b/spec/plugins/response-transformer/big_resonse_body_spec.lua
new file mode 100644
index 000000000000..20d2230cecd9
--- /dev/null
+++ b/spec/plugins/response-transformer/big_resonse_body_spec.lua
@@ -0,0 +1,59 @@
+local spec_helper = require "spec.spec_helpers"
+local http_client = require "kong.tools.http_client"
+local cjson = require "cjson"
+
+local STUB_POST_URL = spec_helper.PROXY_URL.."/post"
+
+local function create_big_data(size)
+  return string.format([[
+    {"mock_json":{"big_field":"%s"}}
+  ]], string.rep("*", size))
+end
+
+describe("Response Transformer Plugin #proxy", function()
+  setup(function()
+    spec_helper.prepare_db()
+    spec_helper.insert_fixtures {
+      api = {
+        {name = "tests-response-transformer", request_host = "response.com", upstream_url = "http://httpbin.org"}
+      },
+      plugin = {
+        {
+          name = "response-transformer",
+          config = {
+            add = {
+              json = {"p1:v1"}
+            },
+            remove = {
+              json = {"json"}
+            }
+          },
+          __api = 1
+        }  
+      }
+    }
+    spec_helper.start_kong()
+  end)
+
+  teardown(function()
+    spec_helper.stop_kong()
+  end)
+  
+  describe("Test add", function()
+    it("should add new parameters on GET", function()
+      local response, status = http_client.post(STUB_POST_URL, {create_big_data(1 * 1024 * 1024)}, {host = "response.com", ["content-type"] = "application/json"})
+      assert.equal(200, status)
+      local body = cjson.decode(response)
+      assert.equal("v1", body["p1"])
+    end)
+  end)
+  
+  describe("Test remove", function()
+    it("should remove parameters on GET", function()
+      local response, status = http_client.post(STUB_POST_URL, {create_big_data(1 * 1024 * 1024)}, {host = "response.com", ["content-type"] = "application/json"})
+      assert.equal(200, status)
+      local body = cjson.decode(response)
+      assert.falsy(body["json"])
+    end)
+  end)
+end)
diff --git a/spec/plugins/response-transformer/body_transformer_spec.lua b/spec/plugins/response-transformer/body_transformer_spec.lua
new file mode 100644
index 000000000000..c2681cdc3fb8
--- /dev/null
+++ b/spec/plugins/response-transformer/body_transformer_spec.lua
@@ -0,0 +1,163 @@
+local body_transformer = require "kong.plugins.response-transformer.body_transformer"
+local cjson = require "cjson"
+
+describe("response-transformer body_transformer", function()
+  describe("transform_json_body()", function()
+    describe("add", function()
+      local conf = {
+        remove = {
+          json = {}
+        },
+        replace = {
+          json = {}
+        },
+        add = {
+          json = {"p1:v1", "p3:v3", "p4:\"v1\""}
+        },
+        append = {
+          json = {}
+        },
+      }
+      it("should add parameter", function()
+        local json = [[{"p2":"v1"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({p1 = "v1", p2 = "v1", p3 = "v3", p4 = '"v1"'}, body_json)
+      end)
+      it("should add value in double quotes", function()
+        local json = [[{"p2":"v1"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({p1 = "v1", p2 = "v1", p3 = "v3", p4 = '"v1"'}, body_json)
+      end)
+    end)
+    
+    describe("append", function()
+      local conf = {
+        remove = {
+          json = {}
+        },
+        replace = {
+          json = {}
+        },
+        add = {
+          json = {}
+        },
+        append = {
+          json = {"p1:v1", "p3:\"v1\""}
+        },
+      }
+      it("should add new key:value if key does not exists", function()
+        local json = [[{"p2":"v1"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({ p2 = "v1", p1 = {"v1"}, p3 = {'"v1"'}}, body_json)
+      end)
+      it("should append value if key exists", function()
+        local json = [[{"p1":"v2"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({ p1 = {"v2","v1"}, p3 = {'"v1"'}}, body_json)
+      end)
+      it("should append value in double quotes", function()
+        local json = [[{"p3":"v2"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({p1 = {"v1"}, p3 = {"v2",'"v1"'}}, body_json)
+      end)
+    end)
+    
+    describe("remove", function()
+      local conf = {
+        remove = {
+          json = {"p1", "p2"}
+        },
+        replace = {
+          json = {}
+        },
+        add = {
+          json = {}
+        },
+        append = {
+          json = {}
+        }
+      }
+      it("should remove parameter", function()
+        local json = [[{"p1" : "v1", "p2" : "v1"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        assert.equal("{}", body)
+      end)
+    end)
+    
+    describe("replace", function()
+      local conf = {
+        remove = {
+          json = {}
+        },
+        replace = {
+          json = {"p1:v2", "p2:\"v2\""}
+        },
+        add = {
+          json = {}
+        },
+        append = {
+          json = {}
+        }
+      }
+      it("should replace parameter if it exists", function()
+        local json = [[{"p1" : "v1", "p2" : "v1"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({p1 = "v2", p2 = '"v2"'}, body_json)
+      end)
+      it("should not add value to parameter if parameter does not exists", function()
+        local json = [[{"p1" : "v1"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({p1 = "v2"}, body_json)
+      end)
+      it("should replce to double quoted value", function()
+        local json = [[{"p2" : "v1"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({p2 = '"v2"'}, body_json)
+      end)
+    end)
+    
+    describe("remove, replace, add, append", function()
+      local conf = {
+        remove = {
+          json = {"p1"}
+        },
+        replace = {
+          json = {"p2:v2"}
+        },
+        add = {
+          json = {"p3:v1"}
+        },
+        append = {
+          json = {"p3:v2"}
+        },
+      }
+      it("should remove `p1` and add `p2'", function()
+        local json = [[{"p1" : "v1", "p2" : "v1"}]]
+        local body = body_transformer.transform_json_body(conf, json)
+        local body_json = cjson.decode(body)
+        assert.same({p2 = "v2", p3 = {"v1", "v2"}}, body_json)
+      end)
+    end)
+  end)
+  
+  describe("is_json_body()", function()
+    it("should be true when content-type application/json passed", function()
+        assert.truthy(body_transformer.is_json_body("application/json"))
+        assert.truthy(body_transformer.is_json_body("application/json; charset=utf-8"))
+    end)
+    it("should be true when content-type is multiple values along with application/json passed", function()
+        assert.truthy(body_transformer.is_json_body("application/x-www-form-urlencoded, application/json"))
+    end)
+    it("should be fail when content-type not application/json", function()
+        assert.falsy(body_transformer.is_json_body("application/x-www-form-urlencoded"))
+    end)
+  end)
+end)
\ No newline at end of file
diff --git a/spec/plugins/response-transformer/filter_spec.lua b/spec/plugins/response-transformer/filter_spec.lua
index 189a3d6c3f9f..b9698219de79 100644
--- a/spec/plugins/response-transformer/filter_spec.lua
+++ b/spec/plugins/response-transformer/filter_spec.lua
@@ -3,41 +3,25 @@ local http_client = require "kong.tools.http_client"
 local cjson = require "cjson"
 
 local STUB_GET_URL = spec_helper.PROXY_URL.."/get"
-local STUB_POST_URL = spec_helper.PROXY_URL.."/post"
 local STUB_HEADERS_URL = spec_helper.PROXY_URL.."/response-headers"
 
 describe("Response Transformer Plugin #proxy", function()
-
   setup(function()
     spec_helper.prepare_db()
     spec_helper.insert_fixtures {
       api = {
-        {name = "tests-response-transformer", request_host = "response.com", upstream_url = "http://httpbin.org"},
-        {name = "tests-response-transformer2", request_host = "response2.com", upstream_url = "http://httpbin.org"}
+        {name = "tests-response-transformer", request_host = "response.com", upstream_url = "http://httpbin.org"}
       },
       plugin = {
         {
           name = "response-transformer",
           config = {
-            add = {
-              headers = {"x-added:true", "x-added2:true"},
-              json = {"newjsonparam:newvalue"}
-            },
             remove = {
-              headers = {"x-to-remove"},
-              json = {"origin"}
+              headers = {"Access-Control-Allow-Origin"},
+              json = {"url"}
             }
           },
           __api = 1
-        },
-        {
-          name = "response-transformer",
-          config = {
-            add = {
-              headers = {"Cache-Control:max-age=86400"}
-            }
-          },
-          __api = 2
         }
       }
     }
@@ -49,52 +33,20 @@ describe("Response Transformer Plugin #proxy", function()
     spec_helper.stop_kong()
   end)
 
-  describe("Test adding parameters", function()
-
-    it("should add new headers", function()
-      local _, status, headers = http_client.get(STUB_GET_URL, {}, {host = "response.com"})
-      assert.are.equal(200, status)
-      assert.are.equal("true", headers["x-added"])
-      assert.are.equal("true", headers["x-added2"])
-    end)
-
-    it("should add new parameters on GET", function()
+  describe("Test transforming parameters", function()
+    it("should remove a parameter", function()
       local response, status = http_client.get(STUB_GET_URL, {}, {host = "response.com"})
-      assert.are.equal(200, status)
-      local body = cjson.decode(response)
-      assert.are.equal("newvalue", body["newjsonparam"])
-    end)
-
-    it("should add new parameters on POST", function()
-      local response, status = http_client.post(STUB_POST_URL, {}, {host = "response.com"})
-      assert.are.equal(200, status)
+      assert.equal(200, status)
       local body = cjson.decode(response)
-      assert.are.equal("newvalue", body["newjsonparam"])
+      assert.falsy(body.url)
     end)
-
-    it("should add new headers", function()
-      local _, status, headers = http_client.get(STUB_GET_URL, {}, {host = "response2.com"})
-      assert.are.equal(200, status)
-      assert.are.equal("max-age=86400", headers["cache-control"])
-    end)
-
   end)
-
-  describe("Test removing parameters", function()
-
+  
+  describe("Test transforming headers", function()  
     it("should remove a header", function()
-      local _, status, headers = http_client.get(STUB_HEADERS_URL, {["x-to-remove"] = "true"}, {host = "response.com"})
-      assert.are.equal(200, status)
-      assert.falsy(headers["x-to-remove"])
+      local _, status, headers = http_client.get(STUB_HEADERS_URL, {}, {host = "response.com"})
+      assert.equal(200, status)
+      assert.falsy(headers["access-control-allow-origin"])
     end)
-
-    it("should remove a parameter on GET", function()
-      local response, status = http_client.get(STUB_GET_URL, {}, {host = "response.com"})
-      assert.are.equal(200, status)
-      local body = cjson.decode(response)
-      assert.falsy(body.origin)
-    end)
-
   end)
-
 end)
diff --git a/spec/plugins/response-transformer/header_transformer_spec.lua b/spec/plugins/response-transformer/header_transformer_spec.lua
new file mode 100644
index 000000000000..c1e476cef735
--- /dev/null
+++ b/spec/plugins/response-transformer/header_transformer_spec.lua
@@ -0,0 +1,189 @@
+local header_transformer = require "kong.plugins.response-transformer.header_transformer"
+local CONTENT_LENGTH = "content-length"
+
+describe("response-transformer header_transformer", function()
+  describe("execute_headers()", function()
+    describe("remove", function()
+      local conf = {
+        remove = {
+          headers = {"h1", "h2", "h3"}
+        },
+        replace = {
+          headers = {}
+        },
+        add = {
+          json = {"p1:v1"},
+          headers = {}
+        },
+        append = {
+          headers = {}
+        }
+      }
+      it("should remove an exisiting header from arg #2", function()
+        local ngx_headers = {h1 = "value1", h2 = {"value2a", "value2b"}}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.same({}, ngx_headers)
+      end)
+      it("should set content-length nil", function()
+        local ngx_headers = {h1 = "value1", h2 = {"value2a", "value2b"}, [CONTENT_LENGTH] = "100", ["content-type"] = "application/json"}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.falsy(ngx_headers[CONTENT_LENGTH])
+      end)
+    end)
+    describe("replace", function()
+      local conf = {
+        remove = {
+          headers = {}
+        },
+        replace = {
+          headers = {"h1:v1", "h2:v2"}
+        },
+        add = {
+          json = {"p1:v1"},
+          headers = {}
+        },
+        append = {
+          headers = {}
+        }
+      }
+      it("should replace a header if the header only exists", function()
+        local req_ngx_headers = {h1 = "value1", h2 = {"value2a", "value2b"}}
+        header_transformer.transform_headers(conf, req_ngx_headers)
+        assert.same({h1 = "v1", h2 = "v2"}, req_ngx_headers)
+      end)
+      it("should not add a new header if the header does not already exist", function()
+        local req_ngx_headers = {h2 = {"value2a", "value2b"}}
+        header_transformer.transform_headers(conf, req_ngx_headers)
+        assert.same({h2 = "v2"}, req_ngx_headers)
+      end)
+      it("should set content-length nil", function()
+        local ngx_headers = {h1 = "value1", h2 = {"value2a", "value2b"}, [CONTENT_LENGTH] = "100", ["content-type"] = "application/json"}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.falsy(ngx_headers[CONTENT_LENGTH])
+      end)
+    end)
+    describe("add", function()
+      local conf = {
+        remove = {
+          headers = {}
+        },
+        replace = {
+          headers = {}
+        },
+        add = {
+          json = {"p1:v1"},
+          headers = {"h2:v2"}
+        },
+        append = {
+          headers = {}
+        }
+      }
+      it("should add a header if the header does not exists", function()
+        local req_ngx_headers = {h1 = "v1"}
+        header_transformer.transform_headers(conf, req_ngx_headers)
+        assert.same({h1 = "v1", h2 = "v2"}, req_ngx_headers)
+      end)
+      it("should not add a new header if the header already exist", function()
+        local req_ngx_headers = {h1 = "v1", h2 = "v3"}
+        header_transformer.transform_headers(conf, req_ngx_headers)
+        assert.same({h1 = "v1", h2 = "v3"}, req_ngx_headers)
+      end)
+      it("should set content-length nil", function()
+        local ngx_headers = {h1 = "v1", [CONTENT_LENGTH] = "100", ["content-type"] = "application/json"}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.falsy(ngx_headers[CONTENT_LENGTH])
+      end)
+    end)
+    describe("append", function()
+      local conf = {
+        remove = {
+          headers = {}
+        },
+        replace = {
+          headers = {}
+        },
+        add = {
+          json = {"p1:v1"},
+          headers = {}
+        },
+        append = {
+          headers = {"h1:v2"}
+        }
+      }
+      it("should add a header if the header does not exists", function()
+        local req_ngx_headers = {}
+        header_transformer.transform_headers(conf, req_ngx_headers)
+        assert.same({"v2"}, req_ngx_headers["h1"])
+      end)
+      it("should append  header if the header already exist", function()
+        local req_ngx_headers = {h1 = "v1"}
+        header_transformer.transform_headers(conf, req_ngx_headers)
+        assert.same({h1 = {"v1", "v2"}}, req_ngx_headers)
+      end)
+      it("should set content-length nil", function()
+        local ngx_headers = {h1 = "v1", [CONTENT_LENGTH] = "100", ["content-type"] = "application/json"}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.falsy(ngx_headers[CONTENT_LENGTH])
+      end)
+    end)
+    describe("performing remove, replace, add, append togeather", function()
+      local conf = {
+        remove = {
+          headers = {"h1:v1"}
+        },
+        replace = {
+          headers = {"h2:v3"}
+        },
+        add = {
+          json = {"p1:v1"},
+          headers = {"h3:v3"}
+        },
+        append = {
+          headers = {"h3:v4"}
+        }
+      }
+      it("should transform all headers", function()
+        local req_ngx_headers = {h1 = "v1", h2 = "v2"}
+        header_transformer.transform_headers(conf, req_ngx_headers)
+        assert.same({h2 = "v3", h3 = {"v3", "v4"}}, req_ngx_headers)
+      end)
+      it("should set content-length nil", function()
+        local ngx_headers = {h1 = "v1", [CONTENT_LENGTH] = "100", ["content-type"] = "application/json"}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.falsy(ngx_headers[CONTENT_LENGTH])
+      end)
+    end)
+    describe("content-type", function()
+      local conf = {
+        remove = {
+          headers = {"h1"}
+        },
+        replace = {
+          headers = {}
+        },
+        add = {
+          json = {},
+          headers = {}
+        },
+        append = {
+          headers = {}
+        }
+      }
+      it("should set content-length nil if application/json passed", function()
+        local ngx_headers = {[CONTENT_LENGTH] = "100", ["content-type"] = "application/json"}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.falsy(ngx_headers[CONTENT_LENGTH])
+      end)
+      it("should set content-length nil if application/json and charset passed", function()
+        local ngx_headers = {[CONTENT_LENGTH] = "100", ["content-type"] = "application/json; charset=utf-8"}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.falsy(ngx_headers[CONTENT_LENGTH])
+      end)
+      it("should not set content-length nil if content-type not json", function()
+        local ngx_headers = {[CONTENT_LENGTH] = "100", ["content-type"] = "application/x-www-form-urlencoded; charset=utf-8"}
+        header_transformer.transform_headers(conf, ngx_headers)
+        assert.equal('100', ngx_headers[CONTENT_LENGTH])
+      end)
+    end)  
+  end)
+end)
\ No newline at end of file
diff --git a/spec/unit/dao/entities_schemas_spec.lua b/spec/unit/dao/entities_schemas_spec.lua
index eed79efc9774..d9abdbbde5a5 100644
--- a/spec/unit/dao/entities_schemas_spec.lua
+++ b/spec/unit/dao/entities_schemas_spec.lua
@@ -293,11 +293,13 @@ describe("Entities Schemas", function()
       local valid = validate_entity(plugin, plugins_schema, {dao = dao_stub})
       assert.same({key_names = {"apikey"}, hide_credentials = false}, plugin.config)
       assert.True(valid)
-
-      -- Insert reauest-transformer, whose default config has no default values, and should be empty
+    end)
+    
+    it("should be valid if no value is specified for subfield and if the config schema has default as empty array", function()
+      -- Insert response-transformer, whose default config has no default values, and should be empty
       local plugin2 = {name = "response-transformer", api_id = "stub"}
-      valid = validate_entity(plugin2, plugins_schema, {dao = dao_stub})
-      assert.same({}, plugin2.config)
+      local valid = validate_entity(plugin2, plugins_schema, {dao = dao_stub})
+      assert.same({remove = {headers = {}}, replace = {headers = {}}, add = {headers = {}},  append = {headers = {}}}, plugin2.config)
       assert.True(valid)
     end)