Add initial specs for pipeline build chain class

spec/lib/gitlab/ci/pipeline/chain/build_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Ci::Pipeline::Chain::Build do
+  set(:project) { create(:project, :repository) }
+  set(:user) { create(:user) }
+  let(:pipeline) { Ci::Pipeline.new }
+
+  let(:command) do
+    double('command', source: :push,
+                      origin_ref: 'master',
+                      checkout_sha: project.commit.id,
+                      after_sha: nil,
+                      before_sha: nil,
+                      trigger_request: nil,
+                      schedule: nil,
+                      project: project,
+                      current_user: user)
+  end
+
+  let(:step) { described_class.new(pipeline, command) }
+
+  before do
+    stub_ci_pipeline_to_return_yaml_file
+
+    step.perform!
+  end
+
+  it 'never breaks the chain' do
+    expect(step.break?).to be false
+  end
+
+  it 'fills pipeline object with data' do
+    expect(pipeline.sha).not_to be_empty
+  end
+
+  it 'sets a valid config source' do
+    expect(pipeline.repository_source?).to be true
+  end
+
+  it 'returns a valid pipeline' do
+    expect(pipeline).to be_valid
+  end
+end