Add tests for deployment and environment entitites

spec/serializers/deployment_entity_spec.rb

+require 'spec_helper'
+
+describe DeploymentEntity do
+  let(:entity) do
+    described_class.new(deployment, request: double)
+  end
+
+  let(:deployment) { create(:deployment) }
+
+  subject { entity.as_json }
+
+  it 'exposes internal deployment id'  do
+    expect(subject).to include(:iid)
+  end
+
+  it 'exposes nested information about branch' do
+    expect(subject[:ref][:name]).to eq 'master'
+    expect(subject[:ref][:ref_url]).not_to be_empty
+  end
+end

spec/serializers/environment_entity_spec.rb

+require 'spec_helper'
+
+describe EnvironmentEntity do
+  let(:entity) do
+    described_class.new(environment, request: double)
+  end
+
+  let(:environment) { create(:environment) }
+  subject { entity.as_json }
+
+  it 'exposes latest deployment' do
+    expect(subject).to include(:last_deployment)
+  end
+
+  it 'exposes core elements of environment' do
+    expect(subject).to include(:id, :name, :state, :environment_url)
+  end
+end