tests: Update the miss handler test

tests/test-miss-handlers.lua

@@ -2,6 +2,7 @@
 
 local class = tag
 local obj = class({})
+local handler = require("gears.object.properties")
 
 awesome.connect_signal("debug::index::miss", error)
 awesome.connect_signal("debug::newindex::miss", error)
@@ -23,4 +24,10 @@ end)
 obj.key = 42
 assert(called)
 
+handler(class, {auto_emit=true})
+
+assert(not obj.key)
+obj.key = 1337
+assert(obj.key == 1337)
+
 require("_runner").run_steps({ function() return true end })