Refact build queue service tests to improve readability

spec/services/ci/update_build_queue_service_spec.rb

@@ -8,76 +8,89 @@ RSpec.describe Ci::UpdateBuildQueueService do
   let(:pipeline) { create(:ci_pipeline, project: project) }
 
   describe '#push' do
-    it 'creates a new pending build in transaction' do
-      transition = double(to: 'pending')
+    let(:transition) { double('transition') }
+
+    before do
+      allow(transition).to receive(:to).and_return('pending')
       allow(transition).to receive(:within_transaction).and_yield
+    end
 
-      queued = subject.push(build, transition)
+    context 'when pending build can be created' do
+      it 'creates a new pending build in transaction' do
+        queued = subject.push(build, transition)
 
-      expect(queued.build).to eq build
-      expect(queued.project).to eq project
-    end
+        expect(queued.build).to eq build
+        expect(queued.project).to eq project
+      end
 
-    it 'increments queue push metric' do
-      metrics = spy('metrics')
-      transition = double(to: 'pending')
-      allow(transition).to receive(:within_transaction).and_yield
+      it 'increments queue push metric' do
+        metrics = spy('metrics')
 
-      described_class.new(metrics).push(build, transition)
+        described_class.new(metrics).push(build, transition)
 
-      expect(metrics)
-        .to have_received(:increment_queue_operation)
-        .with(:build_queue_push)
+        expect(metrics)
+          .to have_received(:increment_queue_operation)
+          .with(:build_queue_push)
+      end
     end
 
-    it 'raises an error when invalid transition is detected' do
-      transition = double(to: 'created')
+    context 'when invalid transition is detected' do
+      it 'raises an error' do
+        allow(transition).to receive(:to).and_return('created')
 
-      expect { subject.push(build, transition) }
-        .to raise_error(described_class::InvalidQueueTransition)
+        expect { subject.push(build, transition) }
+          .to raise_error(described_class::InvalidQueueTransition)
+      end
     end
   end
 
   describe '#pop' do
-    it 'removes pending build in a transaction' do
-      transition = double(from: 'pending')
+    let(:transition) { double('transition') }
+
+    before do
+      allow(transition).to receive(:from).and_return('pending')
       allow(transition).to receive(:within_transaction).and_yield
-      Ci::PendingBuild.create!(build: build, project: project)
+    end
 
-      dequeued = subject.pop(build, transition)
+    context 'when pending build exists' do
+      before do
+        Ci::PendingBuild.create!(build: build, project: project)
+      end
 
-      expect(dequeued.build).to eq build
-      expect(dequeued.project).to eq project
-      expect(dequeued).to be_destroyed
-    end
+      it 'removes pending build in a transaction' do
+        dequeued = subject.pop(build, transition)
 
-    it 'increments queue pop metric' do
-      metrics = spy('metrics')
-      transition = double(from: 'pending')
-      allow(transition).to receive(:within_transaction).and_yield
-      Ci::PendingBuild.create!(build: build, project: project)
+        expect(dequeued.build).to eq build
+        expect(dequeued.project).to eq project
+        expect(dequeued).to be_destroyed
+      end
 
-      described_class.new(metrics).pop(build, transition)
+      it 'increments queue pop metric' do
+        metrics = spy('metrics')
 
-      expect(metrics)
-        .to have_received(:increment_queue_operation)
-        .with(:build_queue_pop)
-    end
+        described_class.new(metrics).pop(build, transition)
 
-    it 'does nothing if there is no pending build to remove' do
-      transition = double(from: 'pending')
-      allow(transition).to receive(:within_transaction).and_yield
+        expect(metrics)
+          .to have_received(:increment_queue_operation)
+          .with(:build_queue_pop)
+      end
+    end
 
-      dequeued = subject.pop(build, transition)
+    context 'when pending build does not exist' do
+      it 'does nothing if there is no pending build to remove' do
+        dequeued = subject.pop(build, transition)
 
-      expect(dequeued).to be_nil
+        expect(dequeued).to be_nil
+      end
     end
 
-    it 'raises an error when invalid transition is detected' do
-      transition = double(from: 'created')
+    context 'when invalid transition is detected' do
+      it 'raises an error' do
+        allow(transition).to receive(:from).and_return('created')
 
-      expect { subject.pop(build, transition) }
-        .to raise_error(described_class::InvalidQueueTransition)
+        expect { subject.pop(build, transition) }
+          .to raise_error(described_class::InvalidQueueTransition)
+      end
     end
   end