diff --git a/files/tests/test_basic.py b/files/tests/test_basic.py
index 676cd78b0..15b017609 100644
--- a/files/tests/test_basic.py
+++ b/files/tests/test_basic.py
@@ -52,3 +52,22 @@ def test_post_and_comment(accounts):
 	post_response = client.get(post.url)
 	assert post_response.status_code == 200
 	assert comment_body in post_response.text
+
+	# yank the ID out again
+	comment = util.ItemData.from_json(submit_comment_response.text)
+
+	# post a comment grandchild!
+	grandcomment_body = util.generate_text()
+	submit_grandcomment_response = client.post("/comment", data={
+		"parent_fullname": comment.id_full,
+		"parent_level": 1,
+		"submission": comment.id,
+		"body": grandcomment_body,
+		"formkey": util.formkey_from(submit_post_response.text),
+	})
+	assert submit_grandcomment_response.status_code == 200
+
+	# verify it actually got posted
+	post_response = client.get(post.url)
+	assert post_response.status_code == 200
+	assert grandcomment_body in post_response.text
diff --git a/files/tests/util.py b/files/tests/util.py
index efc990211..3caf08c18 100644
--- a/files/tests/util.py
+++ b/files/tests/util.py
@@ -1,5 +1,6 @@
 
 from bs4 import BeautifulSoup
+import json
 import random
 import re
 import string
@@ -34,3 +35,20 @@ class ItemData:
         result.id_full = f"t2_{result.id}"
         result.url = url
         return result
+
+    @staticmethod
+    def from_json(text):
+        data = json.loads(text)
+
+        soup = BeautifulSoup(data["comment"], 'html.parser')
+        divid = soup.find("div")["id"]
+
+        match = re.search(r'comment-(\d+)', divid)
+        if match is None:
+            return None
+        
+        result = ItemData()
+        result.id = match.group(1)  	# this really should get yanked out of the JS, not the HTML
+        result.id_full = f"t3_{result.id}"
+        result.url = f"/comment/{result.id}"
+        return result