diff --git a/common/lib/xmodule/xmodule/annotatable_module.py b/common/lib/xmodule/xmodule/annotatable_module.py
index 9e492f755a..665be210e4 100644
--- a/common/lib/xmodule/xmodule/annotatable_module.py
+++ b/common/lib/xmodule/xmodule/annotatable_module.py
@@ -29,14 +29,13 @@ class AnnotatableModule(XModule):
 
         attr = {}
         cls = ['annotatable-span', 'highlight']
-        valid_colors = ['yellow', 'orange', 'purple', 'blue', 'green']
         highlight_key = 'highlight'
-
         color = el.get(highlight_key)
-        if color is not None and color in valid_colors:
-            cls.append('highlight-'+color)
-            attr['_delete'] = highlight_key
 
+        if color is not None:
+            if color in self.highlight_colors:
+                cls.append('highlight-'+color)
+            attr['_delete'] = highlight_key
         attr['value'] = ' '.join(cls)
 
         return { 'class' : attr }
@@ -120,6 +119,7 @@ class AnnotatableModule(XModule):
         self.instructions = self._extract_instructions(xmltree)
         self.content = etree.tostring(xmltree, encoding='unicode')
         self.element_id = self.location.html_id()
+        self.highlight_colors = ['yellow', 'orange', 'purple', 'blue', 'green']
 
 class AnnotatableDescriptor(RawDescriptor):
     module_class = AnnotatableModule
diff --git a/common/lib/xmodule/xmodule/tests/test_annotatable_module.py b/common/lib/xmodule/xmodule/tests/test_annotatable_module.py
index 7a87dcc16d..3a470879e8 100644
--- a/common/lib/xmodule/xmodule/tests/test_annotatable_module.py
+++ b/common/lib/xmodule/xmodule/tests/test_annotatable_module.py
@@ -45,6 +45,70 @@ class AnnotatableModuleTestCase(unittest.TestCase):
             'data-problem-id': {'value': '0', '_delete': 'problem'}
         }
 
-        data_attr = self.annotatable._get_annotation_data_attr(0, el)
-        self.assertTrue(type(data_attr) is dict)
-        self.assertDictEqual(expected_attr, data_attr)
\ No newline at end of file
+        actual_attr = self.annotatable._get_annotation_data_attr(0, el)
+
+        self.assertTrue(type(actual_attr) is dict)
+        self.assertDictEqual(expected_attr, actual_attr)
+
+    def test_annotation_class_attr_default(self):
+        xml = '<annotation title="x" body="y" problem="0">test</annotation>'
+        el = etree.fromstring(xml)
+
+        expected_attr = { 'class': { 'value': 'annotatable-span highlight' } }
+        actual_attr = self.annotatable._get_annotation_class_attr(0, el)
+
+        self.assertTrue(type(actual_attr) is dict)
+        self.assertDictEqual(expected_attr, actual_attr)
+
+    def test_annotation_class_attr_with_valid_highlight(self):
+        xml = '<annotation title="x" body="y" problem="0" highlight="{highlight}">test</annotation>'
+
+        for color in self.annotatable.highlight_colors:
+            el = etree.fromstring(xml.format(highlight=color))
+            value = 'annotatable-span highlight highlight-{highlight}'.format(highlight=color)
+
+            expected_attr = { 'class': {
+                'value': value,
+                '_delete': 'highlight' }
+            }
+            actual_attr = self.annotatable._get_annotation_class_attr(0, el)
+
+            self.assertTrue(type(actual_attr) is dict)
+            self.assertDictEqual(expected_attr, actual_attr)
+
+    def test_annotation_class_attr_with_invalid_highlight(self):
+        xml = '<annotation title="x" body="y" problem="0" highlight="{highlight}">test</annotation>'
+
+        for invalid_color in ['rainbow', 'blink', 'invisible', '', None]:
+            el = etree.fromstring(xml.format(highlight=invalid_color))
+            expected_attr = { 'class': {
+                'value': 'annotatable-span highlight',
+                '_delete': 'highlight' }
+            }
+            actual_attr = self.annotatable._get_annotation_class_attr(0, el)
+
+            self.assertTrue(type(actual_attr) is dict)
+            self.assertDictEqual(expected_attr, actual_attr)
+
+    def test_render_annotation(self):
+        expected_html = '<span class="annotatable-span highlight highlight-yellow" data-comment-title="x" data-comment-body="y" data-problem-id="0">z</span>'
+        expected_el = etree.fromstring(expected_html)
+
+        actual_el = etree.fromstring('<annotation title="x" body="y" problem="0" highlight="yellow">z</annotation>')
+        self.annotatable._render_annotation(0, actual_el)
+
+        self.assertEqual(expected_el.tag, actual_el.tag)
+        self.assertEqual(expected_el.text, actual_el.text)
+        self.assertDictEqual(dict(expected_el.attrib), dict(actual_el.attrib))
+
+    def test_extract_instructions(self):
+        xmltree = etree.fromstring(self.sample_text)
+
+        expected_xml = u"<div>Read the text.</div>"
+        actual_xml = self.annotatable._extract_instructions(xmltree)
+        self.assertIsNotNone(actual_xml)
+        self.assertEqual(expected_xml.strip(), actual_xml.strip())
+
+        xmltree = etree.fromstring('<annotatable>foo</annotatable>')
+        actual = self.annotatable._extract_instructions(xmltree)
+        self.assertIsNone(actual)
\ No newline at end of file