Isolate the request store for Sidekiq jobs in test

This makes sure that each Sidekiq job has a clean request store to
work with.

Otherwise the values might leak into each other and we'd be counting
Gitaly-calls that would otherwise be isolated incorrectly.

ee/spec/services/design_management/save_designs_service_spec.rb

@@ -272,7 +272,7 @@ describe DesignManagement::SaveDesignsService do
           expect { run_service }.to change { commit_count.call }.by(1)
         end
 
-        it 'only does 5 gitaly calls', :request_store, :sidekiq_might_not_need_inline do
+        it 'only does 4 gitaly calls', :request_store, :sidekiq_might_not_need_inline do
           service = described_class.new(project, user, issue: issue, files: files)
           # Some unrelated calls that are usually cached or happen only once
           service.__send__(:repository).create_if_not_exists
@@ -281,8 +281,8 @@ describe DesignManagement::SaveDesignsService do
           request_count = -> { Gitlab::GitalyClient.get_request_count }
 
           # An exists?, a check for existing blobs, default branch, an after_commit
-          # callback on LfsObjectsProject, and the creation of commits
-          expect { service.execute }.to change(&request_count).by(5)
+          # callback on LfsObjectsProject
+          expect { service.execute }.to change(&request_count).by(4)
         end
 
         context 'when uploading too many files' do

spec/spec_helper.rb

@@ -303,6 +303,7 @@ RSpec.configure do |config|
         memory_killer: false # This is not a thing we want to do inline in tests
       ).call(chain)
       chain.add DisableQueryLimit
+      chain.insert_after ::Gitlab::SidekiqMiddleware::RequestStoreMiddleware, IsolatedRequestStore
 
       example.run
     end

spec/support/sidekiq_middleware.rb

@@ -31,3 +31,16 @@ class DisableQueryLimit
     end
   end
 end
+
+# When running `Sidekiq::Testing.inline!` each job is using a request-store.
+# This middleware makes sure the values don't leak into eachother.
+class IsolatedRequestStore
+  def call(_worker, msg, queue)
+    old_store = RequestStore.store.dup
+    RequestStore.clear!
+
+    yield
+
+    RequestStore.store = old_store
+  end
+end