Update docs on how to run E2E tests

Make instructions on how to run the E2E tests against GDK more
explicit and easier to find.

doc/development/testing_guide/end_to_end/index.md

@@ -126,6 +126,18 @@ See [Review Apps][review-apps] for more details about Review Apps.
 [helm-chart]: https://gitlab.com/charts/gitlab/
 [cng]: https://gitlab.com/gitlab-org/build/CNG
 
+## How do I run the tests?
+
+There are two main options for running the tests. If you simply want to run the
+existing tests against a live GitLab instance or against a pre-built docker image
+you can use the [GitLab QA orchestrator][gitlab-qa-readme]. See also [examples
+of the test scenarios you can run via the orchestrator](https://gitlab.com/gitlab-org/gitlab-qa/blob/master/docs/what_tests_can_be_run.md#examples).
+
+On the other hand, if you would like to run against a local development GitLab
+environment, you can use the [GitLab Development Kit (GDK)](https://gitlab.com/gitlab-org/gitlab-development-kit/).
+Please refer to the instructions in the [QA README](https://gitlab.com/gitlab-org/gitlab-ce/tree/master/qa/README.md#how-can-i-use-it)
+and the section below.
+
 ## How do I write tests?
 
 In order to write new tests, you first need to learn more about GitLab QA

qa/README.md

@@ -34,8 +34,23 @@ using `package-and-qa` manual action, to test if everything works fine.
 
 ## How can I use it?
 
-You can use GitLab QA to exercise tests on any live instance! For example, the
-following call would login to a local [GDK] instance and run all specs in
+You can use GitLab QA to exercise tests on any live instance! If you don't
+have an instance available you can follow the instructions below to use
+the [GitLab Development Kit (GDK)][GDK].
+This is the recommended option if you would like to contribute to the tests.
+
+### Run the end-to-end tests in a local development environment
+
+Follow the GDK instructions to [prepare](https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/prepare.md)
+and [install](https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/set-up-gdk.md)
+your local GitLab development environment.
+
+Once you have GDK running, switch to the `qa` directory. E.g., if you setup
+GDK to develop in the main `gitlab-ce` repo, the GitLab source code will be
+in a `gitlab` directory and so the end-to-end test code will be in `gitlab/qa`.
+
+From there you can run the tests. For example, the
+following call would login to the GDK instance and run all specs in
 `qa/specs/features`:
 
 ```