Add a Sidebar class to represent the side bar

Start using it throughout the rest of the app instead of the various
instance variables

test/models/sidebar_test.rb

@@ -0,0 +1,29 @@
+require 'test_helper'
+
+class SidebarTest < ActiveSupport::TestCase
+
+  def setup
+    @sidebar = Sidebar.new(users(:admin_user))
+  end
+
+  def test_it_gets_the_active_contexts
+    assert @sidebar.active_contexts == users(:admin_user).contexts.active
+  end
+
+  def test_it_gets_the_hidden_contexts
+    assert @sidebar.hidden_contexts == users(:admin_user).contexts.hidden
+  end
+
+  def test_it_gets_the_active_projects
+    assert @sidebar.active_projects == users(:admin_user).projects.active
+  end
+
+  def test_it_gets_the_hidden_projects
+    assert @sidebar.hidden_projects == users(:admin_user).projects.hidden
+  end
+
+  def test_it_gets_the_completed_projects
+    assert @sidebar.completed_projects == users(:admin_user).projects.completed
+  end
+
+end