Add controller test

spec/controllers/projects/mattermosts_controller_spec.rb

+require 'spec_helper'
+
+describe Projects::MattermostsController do
+  let!(:project) { create(:empty_project) }
+  let!(:user) { create(:user) }
+
+  before do
+    project.team << [user, :master]
+    sign_in(user)
+  end
+
+  describe 'GET #new' do
+    before do
+      get(:new,
+          namespace_id: project.namespace.to_param,
+          project_id: project.to_param)
+    end
+
+    it 'accepts the request' do
+      expect(response).to have_http_status(200)
+    end
+  end
+
+  describe 'POST #create' do
+    let(:mattermost_params) { { trigger: 'http://localhost:3000/trigger', team_id: 'abc' } }
+
+    subject do
+      post(:create,
+           namespace_id: project.namespace.to_param,
+           project_id: project.to_param,
+           mattermost: mattermost_params)
+    end
+
+    context 'no request can be made to mattermost' do
+      it 'shows the error' do
+        expect(controller).to set_flash[:alert].to /\AFailed to open TCP connection to/
+      end
+    end
+
+    context 'the request is succesull' do
+      before do
+        allow_any_instance_of(Mattermost::Command).to receive(:create).and_return('token')
+      end
+
+      it 'redirects to the new page' do
+        subject
+        service = project.services.last
+
+        expect(subject).to redirect_to(edit_namespace_project_service_url(project.namespace, project, service))
+      end
+    end
+  end
+end