Allow testing on Gitaly call count

Previous efforts were aimed at detecting N + 1 queries, general
regressions are hard to find and mitigate.

doc/development/gitaly.md

@@ -79,6 +79,34 @@ end
 
 Once the code is wrapped in this block, this code-path will be excluded from n+1 detection.
 
+## Request counts
+
+Commits and other git data, is now fetched through Gitaly. These fetches can,
+much like with a database, be batched. This improves performance for the client
+and for Gitaly itself and therefore for the users too. To keep performance stable
+and guard performance regressions, Gitaly calls can be counted and the call count
+can be tested against:
+
+```ruby
+describe 'Gitaly Request count tests' do
+  context 'when the request store is activated', :request_store do
+    it 'correctly counts the gitaly requests made' do
+      count = gitaly_request_count { subject }
+
+      expect { subject }.to change { Gitlab::GitalyClient.get_request_count }.by(10)
+    end
+  end
+
+  context 'when the request store is disabled' do
+    it 'is always zero' do
+      subject
+
+      expect(Gitlab::GitalyClient.get_request_count).to be_zero
+    end
+  end
+end
+```
+
 ---
 
 [Return to Development documentation](README.md)

spec/controllers/projects/pipelines_controller_spec.rb

@@ -3,32 +3,36 @@ require 'spec_helper'
 describe Projects::PipelinesController do
   include ApiHelpers
 
-  let(:user) { create(:user) }
-  let(:project) { create(:project, :public) }
+  set(:user) { create(:user) }
+  set(:project) { create(:project, :public, :repository) }
   let(:feature) { ProjectFeature::DISABLED }
 
   before do
     stub_not_protect_default_branch
     project.add_developer(user)
-    project.project_feature.update(
-      builds_access_level: feature)
+    project.project_feature.update(builds_access_level: feature)
 
     sign_in(user)
   end
 
   describe 'GET index.json' do
     before do
-      create(:ci_empty_pipeline, status: 'pending', project: project)
-      create(:ci_empty_pipeline, status: 'running', project: project)
-      create(:ci_empty_pipeline, status: 'created', project: project)
-      create(:ci_empty_pipeline, status: 'success', project: project)
+      branch_head = project.commit
+      parent = branch_head.parent
 
-      get :index, namespace_id: project.namespace,
-                  project_id: project,
-                  format: :json
+      create(:ci_empty_pipeline, status: 'pending', project: project, sha: branch_head.id)
+      create(:ci_empty_pipeline, status: 'running', project: project, sha: branch_head.id)
+      create(:ci_empty_pipeline, status: 'created', project: project, sha: parent.id)
+      create(:ci_empty_pipeline, status: 'success', project: project, sha: parent.id)
+    end
+
+    subject do
+      get :index, namespace_id: project.namespace, project_id: project, format: :json
     end
 
     it 'returns JSON with serialized pipelines' do
+      subject
+
       expect(response).to have_http_status(:ok)
       expect(response).to match_response_schema('pipeline')
 
@@ -39,6 +43,12 @@ describe Projects::PipelinesController do
       expect(json_response['count']['pending']).to eq 1
       expect(json_response['count']['finished']).to eq 1
     end
+
+    context 'when performing gitaly calls', :request_store do
+      it 'limits the Gitaly requests' do
+        expect { subject }.to change { Gitlab::GitalyClient.get_request_count }.by(10)
+      end
+    end
   end
 
   describe 'GET show JSON' do