Run ruby test in heroku application without database - ruby-on-rails

Question

I have one rails API application (App1), which doesn't have any database (no schema.rb file), but i am using some other application's database without adding any heroku postgres addon so when i push this application to heroku, i set the environment variable as DATABASE_URL = [ Database url of App2 ], also i have added some test cases with mini-test and enabled CI in heroku, it will run the test before the deployment but that time i am getting this error
and this is my application.rb
require_relative 'boot'
require "rails"
# Pick the frameworks you want:
require "active_model/railtie"
require "active_job/railtie"
require "active_record/railtie"
require "action_controller/railtie"
require "action_mailer/railtie"
require "action_view/railtie"
require "action_cable/engine"
# require "sprockets/railtie"
require "rails/test_unit/railtie"
# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(*Rails.groups)
module DemoGroup
class Application < Rails::Application
# Initialize configuration defaults for originally generated Rails version.
config.load_defaults 5.1
# Settings in config/environments/* take precedence over those specified here.
# Application configuration should go into files in config/initializers
# -- all .rb files in that directory are automatically loaded.
# Only loads a smaller set of middleware suitable for API only apps.
# Middleware like session, flash, cookies can be added back manually.
# Skip views, helpers and assets when generating a new resource.
config.api_only = true
end
end
is there any way i can run this test in heroku

Answer 1

The correct way to do this is by attaching the Postgres addon from app2 to app1.
Lets say you set DATABASE_URL on app1 to point to the attachment on app2. Heroku then needs to do maintenance - which changes the database url as its shifted to another server. Heroku is nice enough to automatically update DATABASE_URL on app2 - but app1 will be pointing to an invalid url.
This assumes you have the Heroku CLI client installed.
First get a list of the attachments:
$ heroku addons
Remove the default Postgres addon
$ heroku addons:remove heroku-postgresql:dev --app app1
Replace app2 with the name of your application on heroku.
Attach the addon from the other application.
Then attach the Postgres add-on from app2 to app1:
$ heroku addons:attach attachment_name -a app1
Schema.rb
schema.rb is required for ActiveRecord to work properly. If app1 does actually create migrations you can just commit an "empty" schema.rb:
ActiveRecord::Schema.define(version: 0) do
# These are extensions that must be enabled in order to support this database
enable_extension "plpgsql"
end