Add instructions for running reporting functional tests to x-pack REA…

…DME (#22683)

* add instructions

* rest of instructions

* pdf-image requirements

* typo

* add Ubutnu commands

x-pack/README.md

@@ -100,6 +100,36 @@ We also have SAML API integration tests which set up Elasticsearch and Kibana wi
 node scripts/functional_tests --config test/saml_api_integration/config
 ```
 
+#### Running Reporting functional tests
+
+prerequisites:
+The reporting functional tests use [pdf-image](https://www.npmjs.com/package/pdf-image) to convert PDF's pages to png files for image comparisions between generated reports and baseline reports.
+pdf-image requires the system commands `convert`, `gs`, and `pdfinfo` to function. Those can be set up by running the following.
+
+```sh
+//OSX
+brew install imagemagick ghostscript poppler
+
+//Ubutnu
+sudo apt-get install imagemagick ghostscript poppler-utils
+```
+
+To run the reporting functional tests:
+
+Start the test server
+```sh
+// Run from the directory KIBANA_HOME/x-pack
+node scripts/functional_tests_server
+```
+
+Start the test runner
+```sh
+// Run from the directory KIBANA_HOME/x-pack
+node ../scripts/functional_test_runner --config test/reporting/configs/chromium_functional.js
+```
+
+**Note** Configurations from `kibana.dev.yml` are picked up when running the tests. Ensure that `kibana.dev.yml` does not contain any `xpack.reporting` configurations.
+
 #### Developing functional tests
 
 If you are **developing functional tests** then you probably don't want to rebuild Elasticsearch and wait for all that setup on every test run, so instead use this command to build and start just the Elasticsearch and Kibana servers: