Update tests/platform-ci/README.md how to run platform tests

tests/platform-ci/README.md

-Continuous integration tests for the leap_platform code.
+# Continuous integration tests for the leap_platform code
 
-Usage:
+# Setup
 
+    cd tests/platform-ci
     ./setup.sh
+
+# Run syntax checks and test if catalog compiles
+    
     bin/rake test:syntax
-    bin/rake test:catalog
+    bin/rake catalog
 
 For a list of all tasks:
 
     bin/rake -T
 
-To create a virtual provider, run tests on it, then tear it down:
+# Full integration test
+
+You can create a virtual provider using AWS, run tests on it, then tear it down
+when the tests succeed.
+In order to do so, you need to set your AWS credentials as environment variables:
+
+    export AWS_ACCESS_KEY='...'
+    export AWS_SECRET_KEY='...'
+
+If you want to login to this machine during or after the deploy you need to 
+
+    export SSH_PRIVATE_KEY=$(cat ~/.ssh/id_rsa)
+
+then start the deply test with
 
     ./ci-build.sh
+
+# Running tests with docker and gitlab-runner
+
+Another possibility to run the platform tests is to use [gitlab-runner](https://docs.gitlab.com/runner/)
+together with [Docker](https://www.docker.com/).
+
+Export `AWS_ACCESS_KEY`, `AWS_SECRET_KEY` and `SSH_PRIVATE_KEY` as shown above.
+From the root dir of this repo run:
+
+    gitlab-runner exec docker --env AWS_ACCESS_KEY="$AWS_ACCESS_KEY" --env AWS_SECRET_KEY="$AWS_SECRET_KEY" --env SSH_PRIVATE_KEY="$SSH_PRIVATE_KEY" deploy_test
+
+See `.gitlab-ci.yml` for all the different test jobs.
+
+To ssh into the VM you first need to enter the docker container:
+
+    docker exec -u cirunner -it $(docker ps --latest -q) bash
+
+From there you can access the test provider config directory and ssh into the VM:
+
+      cd /builds/project-0/tests/platform-ci/provider/
+      leap ssh citest0