browser_ui/4_verify/pipeline/trigger_matrix_spec.rb | Verify Trigger matrix creates 2 trigger jobs and passes corresponding matrix variables

Steps

1. Log into GitLab
2. Create a project, setup runner for this project.
3. Prepare CI files
   • Parent pipeline: to trigger child pipeline and include matrix trigger (Provider (string) and Stack (array of strings))
   • Child pipeline when triggered will print out environment variables ($PROVIDER and $STACK) from parent pipeline
4. Commit these files to their project accordingly
5. Visit parent project
6. Go to pipeline page and wait for pipeline to succeed
7. Verify that parent pipeline triggers 2 child pipelines (one child pipeline for each stack item)
8. Expand one of the child pipeline
9. Click job 'test_vars' of this child pipeline
10. Verify that job output has the appropriate $PROVIDER and $STACK values
11. Remove runner at teardown.