add the first server-side unit test

Original commit: elastic/x-pack-elasticsearch@d6680ecb57

.eslintrc

@@ -1,13 +1,13 @@
 ---
 parser: babel-eslint
 
+plugins: [ mocha ]
+
 env:
   es6: true
   amd: true
   node: true
   mocha: true
-  browser: true
-
 
 rules:
   block-scoped-var: 2
@@ -67,3 +67,5 @@ rules:
   valid-typeof: 2
   wrap-iife: [ 2, outside ]
   yoda: 0
+  mocha/no-exclusive-tests: 2
+  mocha/handle-done-callback: 2

CONTRIBUTING.md

@@ -13,9 +13,19 @@ git clone https://github.com/elastic/elasticsearch-marvel.git && cd elasticsearc
 npm install
 ```
 - Start it up
-  - Start Elasticsearch, with esvm `esvm --branch 2.1` or with traditionally `bin/elasticsearch`.
+  - Start Elasticsearch, with esvm `esvm --branch <target version>` or traditionally with `bin/elasticsearch`.
-  - Start up the mock Marvel agent with `gulp index`
+  - Start up the mock Marvel agent with `gulp index`.
-  - Start up the filesystem watching of Marvel code and syncing to Kibana's plugin directory with `gulp dev`
+  - Start up the filesystem watching of Marvel code and syncing to Kibana's plugin directory with `gulp dev`.
-  - Finally startup Kibana from that directory run `bin/kibana`
+  - Finally, startup Kibana by running `bin/kibana --dev` from the root of the Kibana project.
-
 - Check it out, navigate to your [Kibana App](http://localhost:5601)
+
+- Run tests
+```
+gulp test
+```
+
+- Debug tests
+Add a `debugger` line to create a breakpoint, and then:
+```
+gulp sync && mocha debug --compilers js:babel/register /pathto/kibana/installedPlugins/marvel/pathto/__test__/testfile.js
+```