Add CalloutsController specs

spec/controllers/callouts_controller_spec.rb

+require 'spec_helper'
+
+describe CalloutsController do
+  let(:user) { create(:user) }
+
+  before do
+    sign_in(user)
+  end
+
+  describe "POST #dismiss" do
+    subject { post :dismiss, feature_name: 'feature_name', format: :json }
+
+    context 'when callout entry does not exist' do
+      it 'should create a callout entry with dismissed state' do
+        expect { subject }.to change { Callout.count }.by(1)
+      end
+
+      it 'should return success' do
+        subject
+
+        expect(response).to have_gitlab_http_status(:ok)
+      end
+    end
+
+    context 'when callout entry already exists' do
+      let!(:callout) { create(:callout, feature_name: 'feature_name', user: user) }
+
+      it 'should update it with a dismissed state' do
+        expect { subject }.to change { callout.reload.dismissed_state }.from(false).to(true)
+      end
+
+      it 'should return success' do
+        subject
+
+        expect(response).to have_gitlab_http_status(:ok)
+      end
+    end
+  end
+end