Merge branch 'feature/improve-async-pipeline-processing' into 'master'

Improve asynchronous pipeline processing

## What does this MR do?

This MR improves asynchronous processing of pipeline.

## Why was this MR needed?

It eliminates some race conditions and improves performance.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing

## What are the relevant issue / merge request numbers?

Related merge request:  !6410  
Extracted from !6411

See merge request !6650

1 files changed, 22 insertions, 0 deletions

diff --git a/spec/workers/update_pipeline_worker_spec.rb b/spec/workers/update_pipeline_worker_spec.rb
new file mode 100644
index 00000000000..fadc42b22f0
--- /dev/null
+++ b/spec/workers/update_pipeline_worker_spec.rb
@@ -0,0 +1,22 @@
+require 'spec_helper'
+
+describe UpdatePipelineWorker do
+  describe '#perform' do
+    context 'when pipeline exists' do
+      let(:pipeline) { create(:ci_pipeline) }
+
+      it 'updates pipeline status' do
+        expect_any_instance_of(Ci::Pipeline).to receive(:update_status)
+
+        described_class.new.perform(pipeline.id)
+      end
+    end
+
+    context 'when pipeline does not exist' do
+      it 'does not raise exception' do
+        expect { described_class.new.perform(123) }
+          .not_to raise_error
+      end
+    end
+  end
+end