How can I add an array object to tags using add_Tag

[trondhindenes]

I have the following logstash snippet:

elseif [Properties][Telemetry] {
	  mutate {
		update => { "logtype" => "telemetry" }
		add_field => {
		  "key" => "%{[Properties][Telemetry][Key]}"
		  "value" => "%{[Properties][Telemetry][Value]}"
		  "component" => "%{[Properties][Component]}"
		  "test_tags" => "%{[Properties][Telemetry][Tags]}" 
		  #"test_tags" => "hello, yello" 
		}
	  }
	  mutate {
		split => { "test_tags" => "," }
	  }
	  mutate {
		strip => [ "test_tags" ]
	  }
	  mutate {
		add_tag => [ "telemetry" ]
		add_tag => [ "%{test_tags}" ]
	  }
	  mutate {
		remove_field => "Properties"
		lowercase => [ "key" ]
	  }
}

The value of [Properties][Telemetry][Tags] is a comma-separated list, and I want each item to end up in "tags" as a separate item. Using split I'm able to get "test_tags" to show up as an array, but no matter what I do I can't seem to add each item of that field to tags using add_tags. Any suggestion welcome! Sample output of my current filter:

{                                                                                                                 
           "Level" => "Information",                                                                              
        "@version" => "1",                                                                                        
      "@timestamp" => "2017-02-01T17:59:33.842Z",                                                                 
          "source" => "C:\\Logstashtest\\logs\\Services.Metadata.MessageHandler-20170201.txt",             
          "fields" => nil,                                                                                        
          "offset" => 2780,                                                                                       
            "type" => "log",                                                                                      
      "input_type" => "log",                                                                                      
           "count" => 1,                                                                                          
            "beat" => {                                                                                           
        "hostname" => "DESKTOP-5E16B28",                                                                          
            "name" => "DESKTOP-5E16B28"                                                                           
    },                                                                                                            
            "tags" => [                                                                                           
        [0] "win2012r2",                                                                                          
        [1] "beats_input_codec_json_applied",                                                                     
        [2] "telemetry",                                                                                          
        [3] "channel:nrk,channel:123,message:AddAssets"                                                           
    ],                                                                                                            
            "host" => "DESKTOP-5E16B28",                                                                          
         "logtype" => "telemetry",                                                                                
            "hour" => "17",                                                                                       
    "computername" => "WM14",                                                                                     
    "messagelevel" => "Information",                                                                              
             "key" => "assetsrecievedonbus",                                                                      
           "value" => 6,                                                                                          
       "component" => "Services.Metadata.MessageHandler",                                                  
       "test_tags" => [                                                                                           
        [0] "channel:nrk",                                                                                        
        [1] "channel:123",                                                                                        
        [2] "message:AddAssets"                                                                                   
    ]                                                                                                             
}

[terje (Terje Sannum)]

ruby {
    code => "
      tags = event.get('tags')
      (tags ||= []).concat(event.get('test_tags'))
      event.set('tags', tags)
    "
}

[trondhindenes]

Thanks! It doesnt work on my test env unfortunately, "concat" is not understood.

[trondhindenes]

The solution turned out to be rather simple:
mutate {
split => { "extra_tags" => "," }
}
mutate {
merge => { "tags" => "extra_tags" }
}