Implement a second round of review comments from @DouweM.

- Don't use `TableReferences` - using `.arel_table` is shorter!
- Move some database-related code to `Gitlab::Database`
- Remove the `MergeRequest#issues_closed` and
  `Issue#closed_by_merge_requests`  associations. They were either
  shadowing or were too similar to existing methods. They are not being
  used anywhere, so it's better to remove them to reduce confusion.
- Use Rails 3-style validations
- Index for `MergeRequest::Metrics#first_deployed_to_production_at`
- Only include `CycleAnalyticsHelpers::TestGeneration` for specs that
  need it.
- Other minor refactorings.

1 files changed, 1 insertions, 1 deletions

diff --git a/spec/services/merge_requests/create_service_spec.rb b/spec/services/merge_requests/create_service_spec.rb
index a0614abcf62..ff6bad6aaba 100644
--- a/spec/services/merge_requests/create_service_spec.rb
+++ b/spec/services/merge_requests/create_service_spec.rb
@@ -108,7 +108,7 @@ describe MergeRequests::CreateService, services: true do
         allow(service).to receive(:execute_hooks)
         merge_request = service.execute
 
-        expect(merge_request.issues_closed).to match_array([first_issue, second_issue])
+        expect(merge_request.reload.closes_issues).to match_array([first_issue, second_issue])
       end
     end
   end