refactor some lua code

rootfs/etc/nginx/lua/test/defer_test.lua

@@ -0,0 +1,20 @@
+package.path = "./rootfs/etc/nginx/lua/?.lua;./rootfs/etc/nginx/lua/test/mocks/?.lua;" .. package.path
+_G._TEST = true
+local defer = require('util.defer')
+
+local _ngx = {
+    shared = {},
+    log = function(...) end,
+    get_phase = function() return "timer" end,
+}
+_G.ngx = _ngx
+  
+describe("Defer", function()
+   describe("to_timer_phase", function()
+    it("executes passed callback immediately if called on timer phase", function()
+        defer.counter = 0
+        defer.to_timer_phase(function() defer.counter = defer.counter + 1 end)
+        assert.equal(defer.counter, 1)
+    end)
+   end)
+end)