Gitlab CI setup with postgis and activerecord-postgis-adapter gem

I am trying to use gitlab ci for running my tests after pushing to a gitlab.com repository. I have a working CI setup in gitlab using postgresql and after adding geometry fields along with activerecord-postgis-adapter gem (it’s a ruby on rails app)I want to edit my gitlab-ci.yml to support postgis. I wasn’t able to find an example for gitlab-ci.yml with postgis enabled. Couldn’t find any documentation on this except for this (https://www.hackzine.org/postgis-on-gitlab-ci.html) but changing my gitlab-ci as suggested resulted in the following error

Bundler::GemRequireError: There was an error while trying to load the gem ‘activerecord-postgis-adapter’.
Gem Load Error is: the scheme postgres does not accept registry part: testuser:@mdillon__postgis (or bad hostname?)

Any help would be very much appreciated.

Try to change __ by -
testuser:@mdillon-postgis