Add locking and test case

db/post_migrate/20220110231420_remove_requirements_management_test_reports_build_id_fk.rb

@@ -7,6 +7,7 @@ class RemoveRequirementsManagementTestReportsBuildIdFk < Gitlab::Database::Migra
 
   def up
     with_lock_retries do
+      execute('LOCK ci_builds, requirements_management_test_reports IN ACCESS EXCLUSIVE MODE')
       remove_foreign_key_if_exists(:requirements_management_test_reports, :ci_builds, name: CONSTRAINT_NAME)
     end
   end

ee/spec/models/requirements_management/test_report_spec.rb

@@ -168,4 +168,9 @@ RSpec.describe RequirementsManagement::TestReport do
       end
     end
   end
+
+  it_behaves_like 'cleanup by a loose foreign key' do
+    let!(:model) { create(:test_report) }
+    let(:parent) { model.build }
+  end
 end