Move dashboard active tab spinach test to rspec

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

features/dashboard/active_tab.feature

-@dashboard
-Feature: Dashboard Active Tab
-  Background:
-    Given I sign in as a user
-
-  Scenario: On Dashboard Home
-    Given I visit dashboard page
-    Then the active main tab should be Home
-    And no other main tabs should be active
-
-  Scenario: On Dashboard Issues
-    Given I visit dashboard issues page
-    Then the active main tab should be Issues
-    And no other main tabs should be active
-
-  Scenario: On Dashboard Merge Requests
-    Given I visit dashboard merge requests page
-    Then the active main tab should be Merge Requests
-    And no other main tabs should be active
-
-  Scenario: On Dashboard Groups
-    Given I visit dashboard groups page
-    Then the active main tab should be Groups
-    And no other main tabs should be active

features/steps/dashboard/active_tab.rb

-class Spinach::Features::DashboardActiveTab < Spinach::FeatureSteps
-  include SharedAuthentication
-  include SharedPaths
-  include SharedSidebarActiveTab
-end

spec/features/dashboard/active_tab_spec.rb

+require 'spec_helper'
+
+RSpec.describe 'Dashboard Active Tab', feature: true do
+  before do
+    login_as :user
+  end
+
+  shared_examples 'page has active tab' do |title|
+    it "#{title} tab" do
+      expect(page).to have_selector('.nav-sidebar li.active', count: 1)
+      expect(find('.nav-sidebar li.active')).to have_content(title)
+    end
+  end
+
+  context 'on dashboard projects' do
+    before do
+      visit dashboard_projects_path
+    end
+
+    it_behaves_like 'page has active tab', 'Projects'
+  end
+
+  context 'on dashboard issues' do
+    before do
+      visit issues_dashboard_path
+    end
+
+    it_behaves_like 'page has active tab', 'Issues'
+  end
+
+  context 'on dashboard merge requests' do
+    before do
+      visit merge_requests_dashboard_path
+    end
+
+    it_behaves_like 'page has active tab', 'Merge Requests'
+  end
+
+  context 'on dashboard groups' do
+    before do
+      visit dashboard_groups_path
+    end
+
+    it_behaves_like 'page has active tab', 'Groups'
+  end
+end