Check against type explicit, feedback:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347/diffs#note_13173368
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347/diffs#note_13173370

spec/models/build_spec.rb

@@ -687,8 +687,9 @@ describe Ci::Build, models: true do
       end
 
       it 'returns empty relation if the build cannot be found' do
-        builds = project.latest_successful_builds_for('TAIL').all
+        builds = project.latest_successful_builds_for('TAIL')
 
+        expect(builds).to be_kind_of(ActiveRecord::Relation)
         expect(builds).to be_empty
       end
     end
@@ -699,8 +700,9 @@ describe Ci::Build, models: true do
       end
 
       it 'returns empty relation' do
-        builds = project.latest_successful_builds_for('fix').all
+        builds = project.latest_successful_builds_for('fix')
 
+        expect(builds).to be_kind_of(ActiveRecord::Relation)
         expect(builds).to be_empty
       end
     end