Introduce Pattern Library test pages (take two)

FEDX-93

These are developer only pages, so can not be seen in production
environment. On devstack, you can access these pages in LMS and
Studio at:

    /template/ux/reference/pattern-library-test.html

This is the second attempt to enable the Pattern Library. The
first attempt broke Django Templates and didn't work correctly
with right-to-left styling.

common/djangoapps/pipeline_mako/tests/test_render.py

@@ -1,7 +1,12 @@
 """ Tests for rendering functions in the mako pipeline. """
 
+import ddt
+from unittest import skipUnless
+
+from django.conf import settings
 from django.test import TestCase
-from pipeline_mako import render_require_js_path_overrides
+
+from pipeline_mako import render_require_js_path_overrides, compressed_css, compressed_js
 
 
 class RequireJSPathOverridesTest(TestCase):
@@ -31,3 +36,43 @@ class RequireJSPathOverridesTest(TestCase):
         result = render_require_js_path_overrides(self.OVERRIDES)
         # To make the string comparision easy remove the whitespaces
         self.assertEqual(map(str.strip, result.splitlines()), self.OVERRIDES_JS)
+
+
+@ddt.ddt
+class PipelineRenderTest(TestCase):
+    """Test individual pipeline rendering functions. """
+
+    @skipUnless(settings.ROOT_URLCONF == 'lms.urls', 'Test only valid in LMS')
+    @ddt.data(
+        (True,),
+        (False,),
+    )
+    def test_compressed_css(self, pipeline_enabled):
+        """
+        Verify the behavior of compressed_css, with the pipeline
+        both enabled and disabled.
+        """
+        with self.settings(PIPELINE_ENABLED=pipeline_enabled):
+            # Verify the default behavior
+            css_include = compressed_css('style-main-v1')
+            self.assertIn(u'lms-main-v1.css', css_include)
+
+            # Verify that raw keyword causes raw URLs to be emitted
+            css_include = compressed_css('style-main-v1', raw=True)
+            self.assertIn(u'lms-main-v1.css?raw', css_include)
+
+    @skipUnless(settings.ROOT_URLCONF == 'lms.urls', 'Test only valid in LMS')
+    def test_compressed_js(self):
+        """
+        Verify the behavior of compressed_css, with the pipeline
+        both enabled and disabled.
+        """
+        # Verify that a single JS file is rendered with the pipeline enabled
+        with self.settings(PIPELINE_ENABLED=True):
+            js_include = compressed_js('base_application')
+            self.assertIn(u'lms-base-application.js', js_include)
+
+        # Verify that multiple JS files are rendered with the pipeline disabled
+        with self.settings(PIPELINE_ENABLED=False):
+            js_include = compressed_js('base_application')
+            self.assertIn(u'/static/js/src/logger.js', js_include)