I don't think ESIntegTest case is really the way to go - @dadoonet's comment about about running Elasticsearch as part of your build is much more likely to work. ESIntegTestCase is really for testing Elasticsearch or your own plugins. The painless plugin jars aren't available in central to install to test against, iirc. You can get them from the zip/tar/rpm/deb distributions and extract them and use them, but that is brittle and a lot of work so it is probably better to test against an Elasticsearch outside of the test process, hopefully started by the build using the instructions in @dadoonet's post.