No tests / Tests missing

[jordansissel]

(This issue was originally filed by @colinsurprenant at elastic/logstash#1536)

---

per #1270

[purbon]

Hi,
this plugin has no test at all, this is a situation that should be amended soon, so for example changes in both the plugin or the logstash core himself, are properly tested in the CI environment.

If you are giving this plugin some test, feel free to update elastic/logstash#3740 so we keep track of it.