diff --git a/xblocks_contrib/word_cloud/tests/test_word_cloud.py b/xblocks_contrib/word_cloud/tests/test_word_cloud.py
index acbd4cdb..306ecca7 100644
--- a/xblocks_contrib/word_cloud/tests/test_word_cloud.py
+++ b/xblocks_contrib/word_cloud/tests/test_word_cloud.py
@@ -1,14 +1,48 @@
 """
 Tests for WordCloudBlock
 """
+import json
 
 from django.test import TestCase
+from fs.memoryfs import MemoryFS
+from lxml import etree
+from webob import Request
+from xblock.exceptions import NoSuchHandlerError
 from xblock.fields import ScopeIds
 from xblock.test.toy_runtime import ToyRuntime
 
 from xblocks_contrib import WordCloudBlock
 
 
+class _FakeUsageKey(str):
+    """
+    A minimal stand-in for a real opaque_keys UsageKey: it behaves like the
+    plain string ToyRuntime's key-value store expects, while also exposing
+    the ``block_type``/``block_id`` attributes that LegacyXmlMixin's XML
+    export code reads off ``self.usage_key``.
+    """
+
+    def __new__(cls, block_type, block_id):
+        obj = super().__new__(cls, f'{block_type}.{block_id}')
+        obj.block_type = block_type
+        obj.block_id = block_id
+        return obj
+
+
+class WordCloudTestRuntime(ToyRuntime):  # pylint: disable=abstract-method
+    """
+    ToyRuntime extended with the minimal filesystem/policy hooks that
+    LegacyXmlMixin needs to run an OLX import/export cycle.
+    """
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.export_fs = MemoryFS()
+
+    def get_policy(self, usage_id):  # pylint: disable=unused-argument
+        return {}
+
+
 class TestWordCloudBlock(TestCase):
     """Tests for WordCloudBlock"""
 
@@ -89,3 +123,97 @@ def test_prepare_words(self):
         self.assertEqual(result[1]["text"], "world")
         self.assertEqual(result[1]["size"], 2)
         self.assertEqual(result[1]["percent"], 40)
+
+    def test_indexibility(self):
+        """Test indexibility of Word Cloud."""
+        self.block.display_name = "Word Cloud Block"
+        self.block.instructions = "Enter some random words that comes to your mind"
+        self.assertEqual(
+            self.block.index_dictionary(),
+            {
+                'content_type': 'Word Cloud',
+                'content': {
+                    'display_name': 'Word Cloud Block',
+                    'instructions': 'Enter some random words that comes to your mind',
+                },
+            }
+        )
+
+    def test_xml_import_export_cycle(self):
+        """Test the OLX import/export round trip."""
+        runtime = WordCloudTestRuntime()
+
+        original_xml = (
+            '<word_cloud display_name="Favorite Fruits" display_student_percents="false" '
+            'instructions="What are your favorite fruits?" num_inputs="3" num_top_words="100"/>\n'
+        )
+        olx_element = etree.fromstring(original_xml)
+        usage_key = _FakeUsageKey('word_cloud', 'block_id')
+        keys = ScopeIds(None, 'word_cloud', 'def_id', usage_key)
+        block = WordCloudBlock.parse_xml(olx_element, runtime, keys)
+
+        self.assertEqual(block.display_name, 'Favorite Fruits')
+        self.assertFalse(block.display_student_percents)
+        self.assertEqual(block.instructions, 'What are your favorite fruits?')
+        self.assertEqual(block.num_inputs, 3)
+        self.assertEqual(block.num_top_words, 100)
+
+        node = etree.Element('unknown_root')
+        # This will export the olx to a separate file.
+        block.add_xml_to_node(node)
+
+        with runtime.export_fs.open('word_cloud/block_id.xml') as f:
+            exported_xml = f.read()
+
+        self.assertEqual(exported_xml, original_xml)
+
+    def test_bad_dispatch_request(self):
+        """
+        Make sure that dispatching to an unknown handler raises the expected error.
+        """
+        request = Request.blank('/')
+        request.method = 'POST'
+        request.body = json.dumps({}).encode('utf-8')
+        with self.assertRaises(NoSuchHandlerError):
+            self.block.handle('bad_dispatch', request)
+
+    def test_handle_submit_state_request(self):
+        """
+        Make sure that the handle_submit_state AJAX handler works correctly end-to-end
+        (i.e. through the runtime's handler dispatch, not just by calling submit_state directly).
+        """
+        request = Request.blank('/')
+        request.method = 'POST'
+        request.body = json.dumps({'student_words': ['cat', 'cat', 'dog', 'sun']}).encode('utf-8')
+
+        response = json.loads(self.block.handle('handle_submit_state', request).body.decode('utf8'))
+
+        self.assertEqual(response['status'], 'success')
+        self.assertTrue(response['submitted'])
+        self.assertEqual(response['total_count'], 4)
+        self.assertEqual(response['student_words'], {'cat': 2, 'dog': 1, 'sun': 1})
+
+    def test_submit_studio_edits(self):
+        """
+        Test the submit_studio_edits handler (Studio editor Save button), including
+        boolean field handling for display_student_percents.
+        """
+        submitted_values = {
+            'display_name': "New Word Cloud",
+            'instructions': "This is a Test",
+            'num_inputs': 5,
+            'num_top_words': 10,
+            'display_student_percents': False,
+        }
+        request = Request.blank('/')
+        request.method = 'POST'
+        request.body = json.dumps({'values': submitted_values}).encode('utf-8')
+
+        response = json.loads(self.block.handle('submit_studio_edits', request).body.decode('utf8'))
+        self.assertEqual(response, {'result': 'success'})
+
+        self.assertEqual(self.block.display_name, submitted_values['display_name'])
+        self.assertEqual(self.block.instructions, submitted_values['instructions'])
+        self.assertEqual(self.block.num_inputs, submitted_values['num_inputs'])
+        self.assertEqual(self.block.num_top_words, submitted_values['num_top_words'])
+        self.assertIs(self.block.display_student_percents, submitted_values['display_student_percents'])