diff --git a/scripts/upgrade-tests/docker-compose.yml b/scripts/upgrade-tests/docker-compose.yml
index a127a91b011..6f73a512cd0 100644
--- a/scripts/upgrade-tests/docker-compose.yml
+++ b/scripts/upgrade-tests/docker-compose.yml
@@ -17,6 +17,7 @@ services:
       KONG_TEST_PG_HOST: db_postgres
     volumes:
       - ../../worktree/${OLD_KONG_VERSION}:/kong
+      - ../..:/upgrade-test/latest
     restart: on-failure
     networks:
       upgrade_tests:
diff --git a/spec/05-migration/plugins/http-log/migrations/001_280_to_300_spec.lua b/spec/05-migration/plugins/http-log/migrations/001_280_to_300_spec.lua
index 4399aef2a45..54da7f9e9b9 100644
--- a/spec/05-migration/plugins/http-log/migrations/001_280_to_300_spec.lua
+++ b/spec/05-migration/plugins/http-log/migrations/001_280_to_300_spec.lua
@@ -3,57 +3,10 @@ local cjson = require "cjson"
 local tablex = require "pl.tablex"
 
 local uh = require "spec/upgrade_helpers"
+local new_helpers = uh.last_helpers
+local http_server = new_helpers.http_server
 
-local HTTP_PORT = 29100
-
--- Copied from 3.x helpers.lua
-
-local function http_server(port, opts)
-  local threads = require "llthreads2.ex"
-  opts = opts or {}
-  local thread = threads.new(
-    {
-      function(port, opts)
-        local socket = require "socket"
-        local server = assert(socket.tcp())
-        server:settimeout(opts.timeout or 60)
-        assert(server:setoption('reuseaddr', true))
-        assert(server:bind("*", port))
-        assert(server:listen())
-        local client = assert(server:accept())
-
-        local lines = {}
-        local line, err
-        repeat
-          line, err = client:receive("*l")
-          if err then
-            break
-          else
-            table.insert(lines, line)
-          end
-        until line == ""
-
-        if #lines > 0 and lines[1] == "GET /delay HTTP/1.0" then
-          ngx.sleep(2)
-        end
-
-        if err then
-          server:close()
-          error(err)
-        end
-
-        local body, _ = client:receive("*a")
-
-        client:send("HTTP/1.1 200 OK\r\nConnection: close\r\n\r\n")
-        client:close()
-        server:close()
-
-        return lines, body
-      end
-    },
-    port, opts)
-  return thread:start()
-end
+local HTTP_PORT = new_helpers.get_available_port()
 
 describe("http-log plugin migration", function()
 
diff --git a/spec/string_buffer.lua b/spec/string_buffer.lua
new file mode 100644
index 00000000000..fe5e544f378
--- /dev/null
+++ b/spec/string_buffer.lua
@@ -0,0 +1,108 @@
+-- this is a backport of `string.buffer` module of LuaJIT
+-- for older version of Kong code to run tests with new helper functions
+-- this implementation only promise the same behavior as the original but not the same performance
+-- and the methods decode()/encode() are not implemented
+
+local ffi = require "ffi"
+local tbl_new = require "table.new"
+local tbl_clr = require "table.clear"
+
+local _M = {}
+_M.__index = _M
+
+function _M.new(size)
+  local buf = tbl_new(size or 0, 0)
+  buf.n = 0
+  return setmetatable(buf, _M)
+end
+
+function _M:put(...)
+  local n = select("#", ...)
+  if n == 0 then
+    return
+  end
+
+  local buf = self
+  local offset = self.n
+  self.n = offset + n
+
+  for i = 1, n do
+    local item = select(i, ...)
+    buf[offset + i] = tostring(item)
+  end
+
+  return buf
+end
+
+function _M:putf(fmt, ...)
+  return self:put(string.format(fmt, ...))
+end
+
+function _M:putcdata(cdata, len)
+  return self:put(ffi.string(cdata, len))
+end
+
+function _M:set(str, len)
+  self:reset()
+  if len then
+    return self:putcdata(str, len)
+  else
+    return self:put(str)
+  end
+end
+
+function _M:reserve()
+end
+
+function _M:commit()
+end
+
+function _M:reset()
+  tbl_clr(self)
+  self.n = 0
+  return self
+end
+
+function _M:tostring()
+  local result = table.concat(self)
+  self:reset()
+  self[1] = result
+  self.n = 1
+  return result
+end
+
+_M.__tostring = _M.tostring
+
+function _M:ref()
+  return ffi.cast("const char *", self:tostring())
+end
+
+function _M:__len()
+  return #self:tostring()
+end
+
+function _M:skip(len)
+  self[1] = self:tostring():sub(len + 1)
+end
+
+function _M:get(...)
+  local str = self:tostring()
+  local n = select("#", ...)
+
+  local offset = 0
+  local results = {}
+  for i = 1, n do
+    local len = select(i, ...)
+    local result = str:sub(offset + 1, offset + len)
+    offset = offset + len
+    results[i] = result
+  end
+
+  self[1] = str:sub(offset + 1)
+
+  return unpack(results)
+end
+
+_M.free = _M.reset
+
+return _M
diff --git a/spec/upgrade_helpers.lua b/spec/upgrade_helpers.lua
index c7426ee1cde..8f8bd581eef 100644
--- a/spec/upgrade_helpers.lua
+++ b/spec/upgrade_helpers.lua
@@ -1,3 +1,5 @@
+setmetatable(_G, nil)
+
 local say = require "say"
 local assert = require "luassert"
 
@@ -151,6 +153,50 @@ local function all_phases(phrase, f)
   return it_when("all_phases", phrase, f)
 end
 
+local latest_kong_require_meta
+
+-- This is a hack to make the latest kong module and helper functions available to the test suite
+local function latest_kong_require(module)
+  -- backport of `string.buffer` module of LuaJIT
+  if module == "string.buffer" then
+    module = "latest.spec.string_buffer"
+  elseif "kong." == module:sub(1, 5) or "spec." == module:sub(1, 5) then
+    module = "latest." .. module
+  end
+
+  if package.loaded[module] then
+    return package.loaded[module]
+  end
+
+  -- kong module is too heavy to load, and we need to even go through the whole
+  -- build process to get it, so we just return an empty table and leave the functions
+  -- that uses them not implemented
+  if "latest.kong" == module:sub(1, 11) then
+    package.loaded[module] = {}
+    return package.loaded[module]
+  end
+
+  local path = package.searchpath(module, package.path .. ";./?/init.lua")
+
+  -- some buildin modules like ffi don't have a path
+  if not path then
+    return require(module)
+  end
+
+  local module_code = assert(loadfile(path))
+  -- recursively load with lastest code
+  setfenv(module_code, latest_kong_require_meta)
+
+  package.loaded[module] = assert(module_code())
+  
+  return package.loaded[module]
+end
+
+latest_kong_require_meta = { require = latest_kong_require, __index = _G }
+setmetatable(latest_kong_require_meta, latest_kong_require_meta)
+
+local latest_helpers = latest_kong_require "spec.helpers"
+
 return {
   database_type = database_type,
   get_database = get_database,
@@ -164,5 +210,7 @@ return {
   old_after_up = old_after_up,
   new_after_up = new_after_up,
   new_after_finish = new_after_finish,
-  all_phases = all_phases
+  all_phases = all_phases,
+  latest_kong_require = latest_kong_require,
+  latest_helpers = latest_helpers,
 }