The RestHighLevelClient class takes as as an argument a low level client instance RestClient. The first method added is ping, which returns true if the call to HEAD / went ok and false if an IOException was thrown. Any other exception gets bubbled up.
There are two kinds of tests, a unit test (RestHighLevelClientTests) that verifies the interaction between high level and low level client, and an integration test (MainActionIT) which relies on an externally started es cluster to send requests to.
javanna