diff --git a/backend/tests/proposal/test_comment_api.py b/backend/tests/proposal/test_comment_api.py
index 20f940df..d115577e 100644
--- a/backend/tests/proposal/test_comment_api.py
+++ b/backend/tests/proposal/test_comment_api.py
@@ -21,7 +21,16 @@ class TestAPI(BaseUserConfig):
             content_type='application/json'
         )
         self.assertStatus(comment_res, 201)
-    
+
+    def test_invalid_proposal_id_create_comment(self):
+        comment_res = self.app.post(
+            "/api/v1/proposals/12345/comments",
+            data=json.dumps(test_comment),
+            headers=self.headers,
+            content_type='application/json'
+        )
+        self.assertStatus(comment_res, 404)
+
     def test_invalid_signature_create_comment(self):
       proposal = Proposal(
           status="LIVE"
@@ -68,3 +77,29 @@ class TestAPI(BaseUserConfig):
             reply_res.json["parentCommentId"],
             comment_res.json["id"]
         )
+      
+    def test_invalid_parent_comment_id_create_reply(self):
+        proposal = Proposal(
+            status="LIVE"
+        )
+        db.session.add(proposal)
+        db.session.commit()
+        proposal_id = proposal.id
+
+        comment_res = self.app.post(
+            "/api/v1/proposals/{}/comments".format(proposal_id),
+            data=json.dumps(test_comment),
+            headers=self.headers,
+            content_type='application/json'
+        )
+        self.assertStatus(comment_res, 201)
+
+        test_reply_copy = test_reply.copy()
+        test_reply_copy["parentCommentId"] = comment_res.json["id"] + 1
+        reply_res = self.app.post(
+            "/api/v1/proposals/{}/comments".format(proposal_id),
+            data=json.dumps(test_reply_copy),
+            headers=self.headers,
+            content_type='application/json'
+        )
+        self.assertStatus(reply_res, 400)