Add sidenav test to dependencies controller

This commit adds a test to the dependencies controller that checks
if the correct sidenavigation is active.

It also chages a spec helper to support both `response.body` and
`page` objects.

ee/spec/controllers/projects/dependencies_controller_spec.rb

@@ -16,6 +16,8 @@ describe Projects::DependenciesController do
       end
 
       context 'when feature is available' do
+        render_views
+
         before do
           stub_licensed_features(dependency_list: true)
         end
@@ -26,6 +28,12 @@ describe Projects::DependenciesController do
           expect(response).to have_gitlab_http_status(200)
           expect(response).to render_template(:show)
         end
+
+        it 'renders the side navigation with the correct submenu set as active' do
+          subject
+
+          expect(response.body).to have_active_sub_navigation('Dependency List')
+        end
       end
 
       context 'when feature is not available' do

spec/support/matchers/navigation_matcher.rb

@@ -9,6 +9,6 @@ end
 
 RSpec::Matchers.define :have_active_sub_navigation do |expected|
   match do |page|
-    expect(page.find('.sidebar-sub-level-items > li.active:not(.fly-out-top-item)')).to have_content(expected)
+    expect(page).to have_css('.sidebar-sub-level-items > li.active:not(.fly-out-top-item)', text: expected)
   end
 end