Add unit test for `extends` in .gitlab-ci.yml
Add unit test for `extends` in .gitlab-ci.yml

jirutka/gitlabhq,axilleas/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,dreampet/gitlab,iiet/iiet-git,axilleas/gitlabhq,dreampet/gitlab,dreampet/gitlab,jirutka/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,iiet/iiet-git,jirutka/gitlabhq,jirutka/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq